DE102018121942B3 - Ion trap, method for regulating the ion trap and uses to drive an ion trap - Google Patents

Abstract

The present invention relates to an ion trap (1) and an associated method for calibrating an alternating voltage field of an ion trap. The ion trap (1) comprises at least two electrodes (10, 12, 20, 22) that are designed to generate an electric field that has an attractive ponderomotive potential in at least one area, an electric resonator (100) and a vacuum chamber (4). The electrical resonator (100) is set up to supply electrodes (10, 12, 20, 22) of the ion trap (1) with an alternating voltage, the electrical resonator (100) having an oscillating circuit (110), the oscillating circuit (110 ) is arranged within the vacuum chamber (4).

Description

The present invention relates to an ion trap, a method for calibrating an AC field of an ion trap, and uses for driving an ion trap.

The invention relates in particular to the generation of a high-frequency, in particular in the range from 10 to 100 MHz, high voltage, in particular in the range from 100 to over 1000 V, with which an ion trap of the type also known as Paul trap is operated independently of its geometric design, and a associated ion trap. Ion traps which are used in laser spectroscopic applications such as ion trap-based frequency standards or ion trap-based quantum computers are particularly affected.

Especially in laser spectroscopic applications, ion traps have been driven, for example, by resonance transformers made from hand-wound copper air coils in copper cylinders. The intended structure is referred to as a "helical resonator" and is described, for example, by the following specialist article: Siverns, JD [ua]: On the application of radio frequency voltages to ion traps via helical resonators, Applied Physics B (2012), Vol. 107, pp. 921-934 , Described as a "tank circuit", a similar resonator is also used, for example, in the patent application EP 1 509 943 A2 on.

It is also from the published patent application US 2012/0112056 A1 known to build ion traps operated at least at low frequency with an LC resonator from mass-produced components (coil and capacitor), which is also referred to as a "tank circuit". For the present application, this type of control has the disadvantage of a lower current carrying capacity and a lower quality, which limits the advantage described below of control by means of so-called “tank circuits”.

The control by means of a resonance resonant circuit has the advantage of filtering out disturbing electrical noise beyond the drive frequency and of reducing the drive power going into the field of power electronics due to the parasitic capacitances of the ion trap and usually related vacuum bushings.

In the embodiment that maximizes this advantage through high quality, however, this type of control has the disadvantages of a large volume and weight, poor control and stability of the resonance frequency and poor construction suitable for mass production.

It is possible to measure and regulate the amplitude of the voltage thus applied to the ion trap electrodes. So far, this is only known in the obvious embodiment that the voltage sensor is located outside the vacuum chamber in which the ion trap is operated, like the published patent application US 2017/0186595 A1 disclosed.

Other electrodes can be connected to a DC potential. It is state of the art to use an RC low-pass filter for filtering the voltage noise for these electrodes, but not for the electrodes with alternating voltage potential. This low pass can be located outside or inside the vacuum chamber in which the ion trap is operated. The latter was described in Pyka, K. [ua]: A high-precision segmented Paul trap with minimized micromotion for an optical multiple-ion clock, Applied Physics B (2013), Vol. 114, pp. 231-241 ,

The reasons for the design described above are that inductors manufactured as ready-to-buy components generally do not have sufficient qualities and therefore do not allow a resonant circuit built with them, especially not in the field of power electronics. In order to enable low losses and thus high grades, conductors with a high surface area, i.e. ultimately, with a large cross-section, of which only the outermost 1 to 10 micrometers are used due to the skin effect, and high surface quality without a magnetic core material, which is usually lossy. Accordingly, it is a non-trivial problem to find an equally good or better alternative, although air coils can only be made from copper wires up to finger-thick by hand and with considerable manufacturing tolerances.

Ion trap-based quantum computers are usually based on the idea of being able to move ions from one place to another in a large ion trap. Most of the tasks that occur, such as the accumulation of several ions into those ions that are to be moved and splitting all the others, or how to carry out the movement and bring them together with ions that are already at the target location, have sufficient solutions that have already been researched that they are irrelevant to this article. However, this endeavors to provide a large ion trap, which is understood to mean long distances along which ions can be trapped.

A large ion trap, however, will have a large capacity, resulting in unrealizable large ones Currents and performances would lead if they were fed from a single source. A supply from several of the known resonance transformers, on the other hand, is difficult to imagine because their manufacturing tolerances would generally not allow them to be operated synchronously, that is to say at the same frequency and with the correct phase.

This problem has a published but as yet unrealized solution in the scientific article Lekitsch, B. [ua]: Blueprint for a microwave trapped ion quantum computer, Science Advances (2017), Vol. 3, e1601540, pp. 1-11 , The idea is a, albeit minor, miniaturization of the known copper air coils and coupling with adjustable trimming capacitors, with which the resonance frequency can be set.

The previously known solutions are all of limited suitability for mass production. Furthermore, a maximum distance to the wall of the vacuum apparatus is limited by the vacuum bushings necessary for each drive of this type. In addition, the dimensions of the drives proposed so far are too large to supply individual electrodes of a linear ion trap with individually controllable AC voltage.

WO 2015/128438 A1 discloses a system for trapping charged or polar particles with a cryostat and a surface electrode trap for trapping charged or polar particles. The surface electrode trap includes a silicon substrate with a front and a back. Planar electrodes are formed on the front of the silicon substrate, which are designed to generate a trapping potential for trapping the charged or polar particles over the planar electrodes. The planar electrodes include a first radio frequency electrode that extends substantially parallel to the front surface of the substrate and is adjacent to and electrically insulated from the first radio frequency electrode. The surface electrode trap is arranged in the cryostat and the cryostat is set up to cool the surface electrode trap at or below a temperature of 150 K.

US 2011/0290995 A1 discloses an apparatus and method for capturing charged particles and performing controlled interactions between them. The device includes a substrate and RF electrodes and dedicated DC electrodes arranged and configured on the substrate to generate a capture potential for capturing the charged particles over the substrate. The RF and dedicated DC electrodes include at least one RF capture electrode configured to operate on RF voltage to contribute to the capture potential, an array of two or more capture site DC electrodes configured to be are biased with a DC voltage to contribute to the capture potential and a first individually controllable RF control electrode disposed between a first pair of the two or more capture site DC electrodes. The first RF control electrode is configured to be individually driven by an adjustable RF voltage so that the trapping potential across and between the first pair of trapping DC electrodes forms separate charge particle traps that are designed to trap charged particles therein when the adjustable RF voltage takes a first value and forms a charged particle interaction trap suitable for performing controlled interactions between charged particles when the adjustable RF voltage takes a second value.

US 2004/0132083 A1 discloses an ion trap device having an ion trap space surrounded by a plurality of electrodes; a time-of-flight mass analyzer for determining a mass-to-charge ratio of ions ejected from the ion capture space; a trapping voltage generator for generating an ion trapping RF voltage on at least one of the plurality of electrodes; an ejection voltage generator for generating an ejection voltage to at least one of the plurality of electrodes to form an electric ion ejection field for ejecting ions trapped in the ion trapping space; and a controller for stopping the ion trapping RF voltage at a time when ions are trapped in the ion trapping space and the ion trapping RF voltage is in a predetermined phase and applying the ion ejection voltage for a predetermined period after stopping the ion trap RF voltage. Here, the predetermined phase and the predetermined period are predetermined so that when the ion trapping RF voltage is stopped at the predetermined phase and the predetermined period has passed, the voltage of the at least one of the electrodes to which the ion trapping voltage is generated is independent of the amplitude of the RF ion trapping voltage when it is stopped becomes an almost fixed value. Thus, the initial kinetic energy of the ejected ions does not vary with the amplitude of the ion input potential before it is terminated, and an accurate determination of the mass-to-charge ratio of the ions is made possible.

US 2017/0221693 A1 discloses an ion trap device having a method of manufacturing the same, comprising a substrate, a first and a second RF electrode bar, first and second DC electrodes on the upper or lower side of the substrate and a laser passageway connected to the ion trap zone from the outside of the first or second side of the substrate. The substrate includes a space ion capture zone defined by the first and second sides of the substrate separated by a distance with respect to the width direction of the ion trap device. The first and the second HF electrode rails are arranged in parallel in the longitudinal direction of the ion trap device. The first RF electrode is located on the top of the first side, the second DC electrode is located on the bottom of the first side, the first DC electrode is located on the top of the second side, and the second RF electrode rail is on the Bottom of the second page arranged.

Against this background, it was an object of the present invention to provide an improved ion trap and, associated with it, an improved method for calibrating an AC voltage field of an ion trap and uses for driving an ion trap.

According to the invention, the object is achieved in a first aspect by an ion trap with at least two electrodes which are designed to generate an electric field, which comprises an attractive ponderomotive potential at least in one area, an electrical resonator and a vacuum chamber. The electrical resonator is set up to supply electrodes of the ion trap with an alternating voltage, and the electrical resonator has an oscillating circuit. The resonant circuit is arranged inside the vacuum chamber. The resonator has at least one element selected from the list consisting of: a quartz crystal, a ceramic filter, a piezoelectric component and a surface acoustic wave filter.

Because the resonant circuit is arranged within the vacuum chamber, there is no need to introduce the alternating voltage generated for operating the electrodes into the vacuum chamber by means of a so-called vacuum bushing. The vacuum feedthrough, which typically comprise coaxial cables with significant capacitance, is a main factor of the parasitic capacitance, which according to the invention is advantageously eliminated. The parasitic capacitance of the vacuum bushing generates a high apparent power, which in turn results in high currents and thick cables. Because the resonant circuit is arranged within the vacuum chamber, the total energy requirement of the ion trap is therefore lower.

The resonant circuit arranged within the vacuum chamber has advantages in terms of the length of lines, but furthermore, because thinner cables are possible, a further miniaturization of the ion trap is possible. In particular, it is possible for the resonant circuit and electronic control of the actual ion trap to be of the same order of magnitude as the electrodes. Accordingly, an almost unlimited series of electrodes and associated control in the sense of modules is possible.

In this context, ion trap is understood to mean the entire device, which is formed from the actual ion trap within which the ions can be held, and their control, AC voltage supply including resonator and driver.

In one embodiment, the ion trap is designed to keep ions of an effective temperature with at most 1 K within the vacuum chamber.

Charged, in particular simply charged, hydrogen-like ions are preferably kept within the vacuum chamber. Simply charged calcium ions are particularly preferred.

The effective temperature is the temperature at which a physical degree of freedom in thermal equilibrium has an average energy which corresponds to the kinetic and potential energy of a degree of freedom of movement of one or more ions in the ion trap. Since this can differ for the different degrees of freedom of movement, the one that takes the lowest value is chosen as the effective temperature for the sake of clarity. In a technically clever design, this usually corresponds, but not necessarily, to the degree of freedom of movement, the residual movement of which most critically limits the function of the device realized by means of the ion trap. In the preferred embodiment, reaching an effective temperature of below or also considerably below 1 K is achieved with laser-optical means, for example and without being restricted to it by means of that in the patent specification US 6,684,645 B2 disclosed method.

As a consequence of the arrangement according to the invention, it is possible to provide resonators with a significantly lower power consumption than was the case with conventional ion traps. For the exemplary case of a quartz crystal, a power consumption of significantly less than 30 W, preferably in the range of less than 1 W and particularly preferably even less than 1 mW, can be expected, a correspondingly low specification being sufficient to guarantee the accuracy.

In one embodiment, the electrical resonator is set up to supply electrodes of the ion trap with an alternating voltage in a frequency range between 1 MHz and 1 GHz.

In one embodiment, the vacuum chamber is set up to maintain an ultra-high vacuum in its interior, in particular to maintain a pressure of between 10 ^-6 mbar and 10 ^-12 mbar and particularly preferably a pressure of at most 10 ^-10 mbar.

In one embodiment, the ion trap has a driver which is set up to drive the electrical resonator and is designed as a high-impedance and / or high-voltage driver.

All suitable electrical circuits or electronic components that are capable of driving the electrical resonator are understood here as drivers. The training as a high-impedance and / or high-voltage driver ensures that the interference of the ion trap drive is low and that the performance of the driver and the resonator is adapted. The driver is preferably arranged within the vacuum chamber.

In one embodiment, the electrical resonator has a frequency-adjusting element. The frequency-adjusting element can take on all designs known to those skilled in the art and is used in particular to compensate for signs of aging, since the electrical resonator typically changes its resonance frequency over time.

In one embodiment, the ion trap furthermore has a control circuit for stabilizing the amplitude of the voltage across electrodes of the ion trap, the control circuit comprising a voltage-sensitive element which is arranged within the vacuum chamber.

In one embodiment, the drive frequency of the ion trap is generated within the vacuum chamber.

After the control circuit comprises a voltage-sensitive element which is arranged within the vacuum chamber, or the drive frequency of the ion trap is generated within the vacuum chamber, the same advantages, namely with regard to the vacuum implementation and line thickness, are achieved as are achieved in the further embodiments according to the invention. The stabilized amplitude of the voltage across the electrodes, or also the generation of the drive frequency, has the consequence that the ponderomotive potential within the ion trap is designed to be particularly precise and stable, so that the ions within the ion trap can be held particularly reliably.

In one embodiment, the resonator is set up to apply the electrodes of the ion trap with an identical frequency and the same or opposite phase, but with different amplitudes.

Because the amplitude of the different electrodes of the ion trap is applied differently, it is possible to adapt the resulting ponderomotive potential, which takes account of the geometry of the arrangement, for example. The amplitude adjustment accordingly makes it possible to carry out an electronic readjustment of the electrical potential. In this embodiment, it is possible in a particularly simple manner that the amplitudes which are applied to the electrodes by the resonator are different.

In one embodiment, the resonator is set up to compensate for a geometric manufacturing deviation of the electrodes by a choice of the amplitudes.

Accordingly, according to the present invention, according to this embodiment, a greater tolerance to manufacturing deviations is made possible by compensating for them by a suitable choice of the amplitudes. Accordingly, the manufacture of the ion trap and in particular of the electrodes can be reduced, since these allow higher manufacturing deviations.

In one embodiment, the ion trap is designed as a linear ion trap in such a way that a potential along a longitudinal axis takes a minimum over a line.

The linear ion trap formed in accordance with this embodiment enables the ions to move along the longitudinal axis along which the potential takes a minimum over a line. This enables a linear movement of the ions in the ion trap along the longitudinal axis. The minimum that the potential assumes along a line in the longitudinal axis is understood to mean that the potential increases with respect to all other directions at the points of the line. It does not necessarily have to be a uniform minimum potential along the line, as long as the potential curve along the line is lower than with respect to another direction.

In one embodiment, the ion trap also has direct current electrodes, the direct current electrodes being configured to additionally an existing, ponderomotive potential, which has an attractive effect along the longitudinal axis, to generate a potential which in this combination has an attractive effect on a point, and in particular, by means of suitable control of the direct current electrodes, to cause a displacement of the point along the longitudinal axis.

Because the displacement of the point to which the attractively acting potential is generated can be adjusted, a movement of the ions in the ion trap is possible in a defined manner in that the direct current electrodes are controlled appropriately. In other words, the point at which the potential is attractive is shifted by the control of the direct current electrodes, which is particularly advantageous for use in quantum computers.

In one embodiment, the ion trap has two intersecting linear axes, the longitudinal axis and a transverse axis, along which the potential assumes a minimum over a line and which intersect at an intersection point.

Due to the longitudinal axis and the transverse axis, which intersect at a crossing point, it is not only possible to move the ions along the longitudinal axis, but also to make a conscious directional decision at the crossing point. This is done by suitable control of the electrodes, which adapt the potential accordingly. By arranging and controlling the electrodes accordingly, the behavior of a quadrupole can be switched, which is geometrically impossible at a crossing point. According to this embodiment, an approximate implementation of the ideal quadrupole is accordingly implemented, which enables the total potential to be adjusted depending on the location. The intersection of the longitudinal axis and the transverse axis can preferably take place at a right angle, that is to say at approximately 90 °, wherein deviating angles between the longitudinal axis and transverse axis are also conceivable.

In one embodiment, at least some of the electrodes are designed as linear electrodes; in this context, a linear electrode is preferably understood as electrodes in which an electrode length is significantly larger, that is to say, for example, by a factor of 5 and more, than the electrode width along the longitudinal or Transverse axis is executed.

In one embodiment, the electrodes are arranged within at least two essentially parallel layers, the region that can be used for capturing the ions being formed in a space between the outermost of the at least two layers.

Essentially parallel layers are understood here to mean that the planes which are described by the layers differ from one another by an angle of preferably less than 10 °, particularly preferably less than 5 ° and in particular at most 1 °. In the case of two parallel layers, the area that can be used for capturing the ions is formed between the two parallel layers. In the event that more than two parallel layers are arranged, the space is correspondingly formed depending on the arrangement of the further layers between the outermost layers.

In one embodiment, diagonally opposite regions of the outermost layers are formed as common poles and directly opposite or adjacent regions as opposite poles of the AC voltage supply of the resonator, so that a quadrupole is formed.

Because a quadrupole alternating field is formed, a reversal of the sign of the voltage will lead to a reversal of the polarity of the electrical potential, so that the associated ponderomotive potential has an attractive effect on the ions between the opposing layers.

In one embodiment, the electrodes have a finger-like structure, each of the fingers being independently controllable by a resonator. The simultaneous activation of a group of not necessarily adjacent finger electrodes by the same resonator is also possible.

In one embodiment, at least one of the groups of fingers comprises fingers that are evenly spaced, adjacent fingers being contained in different groups.

In one embodiment, a first number of resonators is provided, each of the resonators preferably being able to control a group of a plurality of the fingers, the group of fingers which can be controlled by a specific one of the resonators being spaced apart by the first number of fingers, so that at least a number of fingers, which corresponds to the first number minus one, is arranged between every two fingers which are controlled by the same resonator.

The first number of resonators is preferably selected such that an ion only feels the influence of the field of a finger, which is controlled by a specific resonator, predominantly, that is to say that there is a sufficient distance between the ion and all other fingers. This stems from the fact that ions are predominantly located in the fields Feel the fingers in the vicinity so that a parallel control of more distant resonators has no effect on these ions. This grouped arrangement of the resonators preferably serves to reduce the components and thus the complexity of the ion trap.

In one embodiment, an intermediate space is formed between fingers of the finger-like structure. The intermediate space can be formed, for example, by milling, but other manufacturing methods are also conceivable. Here, a connecting web between two opposing fingers can be partially or even completely omitted, so that each of the layers that represents or contains the electrodes would disintegrate into two pieces or into a number of pieces that corresponds to the number of fingers ,

In one embodiment, the intermediate space is at least partially, in particular entirely, metallized. This can minimize the influence of electrical charges, which are typically present on insulators, which may have a negative impact on the ion trap function. Insulators can, for example, be formed on the surfaces designed as an intermediate space according to the invention and below the metallized surfaces.

In particular, individual control of the electrode fingers, even with AC voltage, opens up new possibilities in the design and adaptation of the potential acting in the ion trap.

In one embodiment, the ion trap has a modular structure, in particular a plurality of electrodes and a plurality of resonators can be assembled modularly. This means that the ion trap can be scaled to almost any size and is particularly suitable for use in quantum computers. It is particularly advantageous here that the miniaturization of the resonator which is also possible according to the invention and which is likewise arranged in the vacuum chamber results in a reduction in the space requirement, which then moves approximately in the order of magnitude of the electrodes.

In one embodiment, adjacent modules of electrodes are arranged in the same plane and / or with planes rotated relative to one another by approximately 90 °, a longitudinal axis or a transverse axis of one module preferably corresponding to the longitudinal axis or the transverse axis of the adjacent module. Within the scope of this disclosure, about 90 ° denotes the range of +/- 20 ° by the right angle of 90 °, preferably the range of +/- 10 ° by 90 ° and particularly preferably the range of +/- 5 ° 90 °.

In one embodiment, the adjacent modules are designed in such a way that ions can be moved between adjacent modules along the longitudinal axis or the transverse axis.

The rotation of the planes relative to one another, for example rotated by approximately 90 °, enables a modular structure of the ion trap to allow the electrodes to be stacked in three dimensions and thus not only in one plane. This enables a particularly efficient construction of the ion trap.

In one embodiment, the modules can thus be stacked in three dimensions.

According to a further aspect, the object is achieved according to the invention by a method for calibrating an alternating voltage field of an ion trap according to the first aspect or a configuration of the ion trap described as an embodiment according to the first aspect. The method has the following steps: i) feeding in an AC voltage for driving the ion trap, ii) feeding in an additional AC voltage which is selected such that it matches a vibration frequency of an ion in the ion trap, iii) determining an increased heating rate of the ion in the ion trap due to the additional AC voltage fed in.

The heating rate of an ion, which is also referred to as the heating rate, is the number of motion quanta it gains per unit of time in relation to a quantized motion axis. For example, such an increase is usually given on the basis of a noise power of the electric field at the ion location at its frequency of movement, even if it is regularly a technical goal to keep this heating rate low.

An ion is in an ion trap in an approximately harmonic potential that only allows quantized changes in the state of motion. If necessary, if a plurality of ions are in the potential of the ion trap, their movements are coupled to one another, which requires the basic principle of the quantum computer, namely that an information exchange between these coupled ions is possible. Depending on the temperature of the ions in the ion trap, for example, Doppler cooling or side band cooling is known. Methods for determining the effective temperature of the ions in the ion trap as well as a detailed discussion of the heating rate and the measurement of the heating rate of the ions can be found, for example, in the dissertation by Thomas W. Deuschle with the title "Cold ion crystals in a segmented Paul trap" from the Year 2007.

In one embodiment, the method further comprises repeating the steps of feeding in the AC voltage, feeding in the additional AC voltage and determining the increased heating rate while changing a parameter, in particular a control amplitude of an AC electrode.

In one embodiment, the method further has the following step: calculating an approximate gradient of the heating rate with respect to the change in the parameter by means of the determined heating rates.

In one embodiment, the method further comprises repeating the steps of feeding in the AC voltage, feeding in the additional AC voltage, determining the increased heating rate and calculating the approximate gradient of the heating rate with iterative change of the parameter to find a target value of the parameter, in particular the calculated gradient of the heating rate is minimized.

According to the invention, the method accordingly calibrates the AC field of an ion trap in such a way that a gradient in the heating rate that occurs during a parameter variation is minimized. The target value of the parameter, which can be the control amplitude, for example, has thus been reached. The method according to the invention can preferably be carried out at regular intervals to ensure that the ion trap is optimally calibrated at all times and that the heating rate, which in particular represents a source of error for determining the states of the ions, is minimal. In other words, the heating rate changes very little at the target value of the parameter when the parameter is changed.

Suitable methods are, for example, minimization algorithms, such as the steepest gradient method (“gradient descent method”) or the conjugate gradient method (“conjugate gradient method”) under suitably chosen boundary conditions or with additional costs (“penalties”) for changing amplitudes from distant ones or electrodes having little effect at the ion site, a sufficiently good parameter being found if the gradient is sufficiently small.

Other minimization methods, in particular those that are gradient-free and also function without the approximate determination of gradients, and those that additionally require the determination of a next higher derivative, that is to say the Hesse matrix, can be used advantageously.

According to a further aspect, the object is achieved according to the invention by using a quartz crystal, a ceramic filter, a piezoelectric component and / or a surface acoustic wave filter as an electrical resonator for driving an ion trap.

Such resonators are known and the fact that, according to the invention, these known resonators are used to drive an ion trap results in the advantages described with reference to the ion trap according to the invention. In particular, miniaturization of the drive of the ion trap is made possible, while at the same time a possibility of mass-producing the ion trap the simple and reliable availability of the resonators is guaranteed.

In one embodiment, the resonator is connected directly or indirectly to electrodes of the ion trap.

In one embodiment, the resonator is connected to electrodes of the ion trap by means of one or more electrical capacitances and / or further electronic components.

• 1 schematisch und exemplarisch eine Anordnung von Elektroden einer Ionenfalle,
• 2 schematisch und exemplarisch eine Anordnung von Elektroden einer Ionenfalle,
• 3 schematisch und exemplarisch eine Anordnung von Elektroden einer Ionenfalle,
• 4 schematisch und exemplarisch eine Anordnung von Elektroden einer Ionenfalle,
• 5 schematisch und exemplarisch eine Anordnung von Elektroden einer Ionenfalle,
• 6 schematisch und exemplarisch ein Schaltbild einer bekannten Ionenfalle,
• 7 schematisch und exemplarisch ein Schaltbild einer erfindungsgemäßen Ionenfalle,
• 8 schematisch und exemplarisch eine Anordnung mehrerer Ionenfallenmodule und
• 9 schematisch und exemplarisch eine perspektivische Ansicht der Geometrie der linearen Ionenfalle.

Further advantages and special configurations are described below with reference to the attached figures. Here show:

• 1 schematically and exemplarily an arrangement of electrodes of an ion trap,
• 2 schematically and exemplarily an arrangement of electrodes of an ion trap,
• 3 schematically and exemplarily an arrangement of electrodes of an ion trap,
• 4 schematically and exemplarily an arrangement of electrodes of an ion trap,
• 5 schematically and exemplarily an arrangement of electrodes of an ion trap,
• 6 schematically and exemplarily a circuit diagram of a known ion trap,
• 7 schematically and exemplarily a circuit diagram of an ion trap according to the invention,
• 8th schematically and exemplarily an arrangement of several ion trap modules and
• 9 schematically and exemplarily a perspective view of the geometry of the linear ion trap.

It is not trivial to make something float, because the Earnshaw theorem states that this does not change with the usual potentials (gravity, electrical and - with the exception of diamagnets and the ideal diamagnets and the ideal diamagnets, superconductor magnetic forces) with static (unchanged in time) ) Arranges. One of the well-known ways out is the " Ion cage ”invented quadrupole (ions) fall, which is also called Paul trap after its inventor.

In the context of this patent application, the term “ion trap” is understood to be a generic term for all devices designed to capture charged particles, in particular ions. In addition to the “Paul trap”, also described as a quadrupole trap, there is another, more common type of ion trap, namely the Penning trap. The term ion trap itself is a back translation from English. The term ion cage from the 1950s is no longer used today, at least not in this context.

A quadrupole trap hangs one or more charged particles, for example a charged atom, i.e. an ion, with an alternating electrical field. This works, although each (static) electric field can create at most one unstable equilibrium in at least one spatial direction. This is because the polarity reversal means that a particle that is initially driven away experiences an even higher momentum in the opposite direction, so that, over time, there is a restoring force in every spatial direction. This effective force is a conservative (energy-conserving) force, which is why there is the mathematical construct of an associated potential, the so-called ponderomotive potential.

The preferred electrical alternating field of a Paul trap representative of a general ion trap is the quadrupole field. This is the lowest order field that creates a resetting, ponderomotive potential. The underlying electrical potential can be illustrated as a saddle surface: there is a trough in one spatial direction and a hill in (at least) one spatial direction perpendicular to it, so that a ball balanced on it in the first spatial direction (along the imaginary horse) into the Middle, along another (the connecting line between the imaginary rider legs) would roll further and further out. The polarity reversal of the alternating field would correspond to turning the saddle inside out (difficult to imagine with a fixed saddle); The rotating analog of the saddle around the vertical axis is often used as a working analogy, although there are real demonstration experiments with rotating saddle surfaces.

Historically, attempts have been made to produce extremely good approximations to this ideal quadrupole field, which is why a Paul trap originally consisted of hyperbolic electrodes, corresponding to the equipotential surfaces of a quadrupole field.

1 shows schematically and exemplarily an ion trap 1 with hyperboloidal electrodes 10 . 20 , The electrode 20 that for better recognizability in the exemplary 1 is cut open, forms the opposite pole to the electrodes 10 that are both at the same potential. The (in 1 Drive (not shown) is, for example, a high-frequency and high-voltage AC voltage source, in which care must be taken in practice that such a source with low noise is used for single-ion operation in the region of the vibration frequencies of the trapped ion or ions. Typical electrode spacings range from fractions of a millimeter to a few millimeters. The electrodes are idealized 10 . 20 touch asymptotically.

However, it was probably discovered experimentally that deviations from the quadrupole field for ion traps 1 are suitable. The following 2 . 3 and 4 show examples of such deviations.

In 2 are the electrodes 10 and 20 designed as opposite round wires. Here and below with the electrodes 10 and 20 denotes those electrodes at which the AC voltage for operating the ion trap is polarized in opposite directions 1 is created. In the 2 The ion trap shown can also be classified as a linear ion trap, with ions having a suitable charge-to-mass ratio being held laterally so that they are in the longitudinal direction of the electrodes 10 . 20 forwarded while other charge-to-mass ratios are filtered out. The range of the charge-to-mass ratio with which ions are held laterally can be made as small or small as desired by superimposing a suitably chosen DC voltage.

3 showed schematically and exemplarily an arrangement of electrodes 10 . 20 an ion trap 1 , which is also known as an end cap trap. An advantage of this arrangement, in which both poles of the alternating voltage on two electrodes each 10 . 20 is a better optical access, for example for laser spectroscopy applications.

4 shows schematically and exemplarily another ion trap 1 , which is known as a surface trap and is also used in the field of quantum computers. On a substrate 50 the electrodes are in one plane 10 and 20 , to which the AC potential of the ion trap 1 is created. In addition, shown radially outside the linear electrodes 10 . 20 , DC electrodes 30 , The control of the DC voltage electrodes 30 can be used to hold and move ions along the longitudinal direction L. The expansion of the electrodes 10 . 20 in a direction perpendicular to the The longitudinal direction L is, for example, in the range from 100 μm to 10 mm, in particular in the range from 100 μm to 1 mm. For this purpose, each of the DC electrodes 30 individual DC voltage electrode sections 32 which can be controlled individually and independently of one another or in groups.

One could say that (almost) every electrode geometry forms a (usually sufficient) component of a field belonging to a restoring, ponderomotive potential; even paper clips have already been used as demonstration traps.

In industry and research, of course, electrode geometries optimized for particularly good function are used, which usually, but not always, results in a high quadrupole content and / or high depth (hurdle to escape) in the ponderomotive potential. Further criteria can be, for example, laser beam accessibility or parameter adjustability by means of further control electrodes.

5 shows schematically and exemplarily an ion trap 1 , which are also referred to below as sandwich traps, because two surfaces structured in electrodes face each other the ion trap 1 form. The number of surfaces structured in electrodes is of course not limited to two, and several layers are also conceivable, so that one can also speak more generally of a deep multilayer trap.

In this arrangement, the opposite poles of the AC circuit are the electrodes 10 and 20 , as a result, as in the linear arrangement shown in 2 is shown trained. In addition, the electrodes 10 . 20 with fingers 12 . 22 trained, between which there are spaces 14 , respectively. 24 are located. Every finger 12 , respectively. 22 the finger-like electrodes 10 . 20 can be controlled independently and thus enables particularly precise control of the space between the electrodes 10 . 20 trained potential.

Static electric fields have noise that is inversely proportional to the fourth power of the distance from the electrode. Large electrodes or a large distance of the electron or ion from the metal surface suppresses noise. The spaces are preferably 14 , respectively. 24 between the fingers 12 . 24 milled or otherwise designed and the surfaces fully metallized. The fingers are particularly preferred 12 and 24 operated with the same or counter phase, the amplitude of the applied voltage differing in order to optimize the potential that arises. In particular, at some points of intersection, which are formed from a crossing longitudinal and transverse axis, it is advantageous to operate certain electrodes at least temporarily instead of with an opposite phase with an in phase. There is also in the 5 electrodes labeled with identical reference numbers 10 . 20 , which are diagonally opposite each other, in which the same phase is basically preferred in many versions.

The most common application of ion traps are mass spectrometers. A sample to be examined is ionized in them and either fed into one of the mass filters already mentioned or into an even more traditional ion trap. Depending on the related voltages (AC voltage and superimposed DC voltage), the AC voltage frequency, the dimensions and the geometry of the ion trap, only a certain range of charge-to-mass ratios is trapped in the ion trap or passed on in the mass filter. If the remaining ions are detected while changing this range, the content of ions with a known charge-to-mass ratio can be determined, that is, a (charge-to-mass) spectrogram can be obtained. The dependencies mentioned can be mathematically summarized in two so-called trap parameters; the corresponding equations of motion (which describe the detailed motion in addition to the approximation of the ponderomotive potential) are called Mathieu equations. A graphical representation with the regions (or one of the most interesting main regions) of trap parameters in which ions or other particles can remain trapped is called the stability diagram.

1. 1. Die normalerweise wild durcheinanderwirbelnde Bewegung der Ionen so weit gebremst ist, dass sich feste Abstände und Winkel zwischen den Ionen ausbilden: Es entsteht ein sogenanntes Ionenkristall.
2. 2. Ein bzw. jedes einzelne Ion sich so wenig bewegt, dass Wechselwirkungen mit Laserlicht mathematisch im sogenannten Lamb-Dicke-Bereich liegen: Die Wechselwirkung zwischen Licht- und Vibrationsbewegung zeigt deutlich die Quantisierung der Vibrationsbewegung als Seitenbandmodulation des optischen Spektrums. Dadurch ist (im Grenzfall einer Lage weit innerhalb dieses Bereichs) eine vereinfachte mathematische Beschreibung und beispielsweise ein weiteres Kühlen durch optische Anregung eines sogenannten Bewegungsseitenbandes möglich. In diesem Grenzfall funktionieren sogenannte „warme“ (oder, nach den Erfindern, Mølmer-Sørensen-) Quantencomputeroperationen (oder, kurz, Quantengatter).
3. 3. Das oder die Ionen praktisch keine Restbewegung mehr aufweisen: Der quatenmechanische Grundzustand (in Bezug auf mindestens eine interessierende Achse der Vibrationsbewegungen) ist erreicht. In diesem Bereich funktionieren sogenannte „kalte“ (oder, nach den Erfindern, Cirac-Zoller-) Quantengatter.

Another application of ion traps is of interest for ion trap-based quantum computers, for example, but also for optical atomic clocks and similar applications: Instead of very many ions, only single or small numbers of ions are caught. The interaction of one or more ions with laser or microwave fields is of interest here. The task of the ion trap is to keep the ion or ions well isolated from the environment in a vacuum, especially in an ultra-high vacuum. It is of particular interest to cool ions so much that (in order of decreasing residual temperature or movement of the ion or ions):

1. 1. The usually wildly swirling movement of the ions is slowed down to such an extent that fixed distances and angles between the ions form: a so-called ion crystal is formed.
2. 2. One or each individual ion moves so little that interaction with laser light is mathematically Thickness range: The interaction between light and vibration movement clearly shows the quantization of the vibration movement as sideband modulation of the optical spectrum. As a result, a simplified mathematical description and, for example, further cooling by optical excitation of a so-called movement sideband is possible (in the limit case of a position far within this range). In this borderline case, so-called “warm” (or, according to the inventors, Mølmer-Sørensen-) quantum computer operations (or, in short, quantum gates) work.
3. 3. That the ion (s) have practically no residual movement: The basic quatomechanical state (in relation to at least one axis of interest of the vibration movements) has been reached. So-called “cold” (or, according to the inventors, Cirac-Zoller) quantum gates work in this area.

In order to enable such ion cooling and to keep ions cooled in this way as cold as long as possible, their movement must not be stimulated too much by electrical interference fields. For example, an alternating electric field at the frequency at which the ion can naturally vibrate in the ponderomotive potential would lead to a resonance effect and thus a high (ion) heating rate. This heating rate is usually measured in quanta of the described vibration (previously also called vibration movement) per unit of time.

The usually strongest source of heating electrical interference fields are field fluctuations that are not scientifically understood in detail, but are related to local effects on electrode surfaces; they decrease sharply with increasing electrode spacing and can be reduced by several orders of magnitude by cleaning (with strong laser pulses or by treatment with argon ions) and by cooling the electrodes to cryogenic temperatures. In the project relevant to this document, they are limited to approximately 1 quantum per second by choosing a relatively large ion trap, in which the minimum distances between ions and electrodes of approximately 500 μm are maintained. Typical for the mostly considerably smaller surface traps often used for ion trap-based quantum computer experiments are heating rates in the order of 1000 quanta per second.

• • Erstens sind die notwendigerweise gemachten Kompromisse bei den Ionenfallenparametern für Einzelionenexperimente in der Regel dann günstiger, wenn man zu hohen Spannungen (oft 100 bis über 1000 V Wechselspannungsamplitude) bei gleichzeitig halbwegs hohen Frequenzen (oft 10 bis 200 MHz) geht. Das hat atomphysikalische Gründe. Durch die schwer unter ca. 20 pF haltbare Kapazität von den üblicherweise verwendeten, elektrischen Koaxialdurchführungen für Ultrahochvakuumsaperaturen entspricht dies Hochleistungselektronik mit Blindleistungen bis jenseits von 1 kVA. Um solche Ionenfallen nicht mit teilweise mehr als 1 kW echter Leistung betreiben zu müssen, ergänzt man diese Kapazität mit einer Induktivität zu einem Schwingkreis mit hoher Güte (typ. sind Gütefaktoren von mehreren hundert bis rund eintausend). Der Resonator wirkt dabei wie ein Leistungsrecycler.
• • Zweitens filtert ein Resonator auch technisches und sogar thermodynamisch unvermeidbares Rauschen. Dies liegt daran, dass elektrische Leistung mit Frequenzen nahe der Resonanz durch den Resonanzeffekt überhöht, andere hingegen abgeschwächt werden. Somit kann die Resonanzüberhöhung für das Recyceln elektrischer Leistung zwischen Schwingungsperioden genutzt werden und gleichzeitig das Rauschen bei den Vibrationsfrequenzen eines oder mehrerer Ionen in der Falle erheblich reduziert werden.

So that field fluctuations generated by electrically applied voltages ideally do not make even larger, but in any case small, additional contributions to the heating rate, high-quality resonators are used as part of the AC voltage supply for ion traps for single ion applications. This is considered necessary for two reasons in particular:

• • Firstly, the compromises that are necessarily made in the ion trap parameters for single ion experiments are generally more favorable if one goes to high voltages (often 100 to over 1000 V AC amplitude) and at the same time reasonably high frequencies (often 10 to 200 MHz). There are atomic-physical reasons for this. Due to the capacity of the commonly used electrical coaxial feedthroughs for ultra-high vacuum apparatuses, which is difficult to maintain below approx. 20 pF, this corresponds to high-performance electronics with reactive powers of up to 1 kVA. In order not to have to operate such ion traps with real power of more than 1 kW in some cases, this capacitance is supplemented with an inductance to form a resonant circuit of high quality (quality factors are typically from several hundred to around one thousand). The resonator acts like a performance recycler.
• Second, a resonator also filters out technical and even thermodynamically unavoidable noise. This is because electrical power with frequencies near the resonance is exaggerated by the resonance effect, while others are weakened. Thus, the resonance increase can be used for the recycling of electrical power between oscillation periods and at the same time the noise at the vibration frequencies of one or more ions in the trap can be considerably reduced.

6 shows schematically and exemplarily a circuit diagram of a conventional drive 80 an ion trap 1 , A signal generator 82 generates an AC voltage from an amplifier 84 is amplified and in a resonance transformer 86 , which is to be understood as two coupled inductors, impedance-converted and filtered. The real area of the ion trap 1 , in which the ions are ultimately trapped, is here with an equivalent circuit, a capacitor 2 shown.

A vacuum chamber 4 is with dashed lines on the right in the illustration of the 6 shown and in any case encloses the as a capacitor 2 shown area in which the ion or ions are trapped. Via a vacuum feedthrough 88 , which has a significant capacity due to its design, the drive power is inside the vacuum chamber 4 guided.

7 shows schematically and exemplarily a circuit of an ion trap according to the invention 1 by a modified resonator 100 is driven. The resonator 100 includes an oscillating circuit 110 which is particularly within the vacuum chamber 4 is arranged. That of the invention underlying concept is therefore that the resonator 100 is integrated into the vacuum, especially the ultra-high vacuum. This saves long lines and the associated capacities, so that compared to the previously known ion traps 1 reactive power is expected to be reduced by an order of magnitude.

According to the invention, this is coupled with the mass-produced resonant circuits 110 , which are normally used exclusively in small signal operation, are used in the field of power electronics in the field of ion trap voltage supply. In particular, the resonator 100 for this purpose a quartz crystal, a ceramic resonator, a ceramic filter, a piezoelectric component, a surface acoustic wave filter and / or a MEMS component. The resonator 100 is used in this embodiment by a high voltage driver 120 through a capacitor 130 fed. The supply from the high voltage driver 120 by means of the capacitor 130 is only to be understood as a possible, but not a necessary implementation.

Accordingly, the resonance transformers commonly used up to now are replaced by one of the resonant resonant circuits described 100 replaced that inside the vacuum chamber 4 to be ordered. The driver, which otherwise operates at a low voltage, is preferably designed as a high-impedance and high-voltage driver.

There should be nonlinearities in the resonators 100 come, this can be noticed, for example, by an amplitude-dependent resonance frequency. Analogous to the suggestion by Lekitsch et al. a frequency-adjusting element and a control circuit for amplitude stabilization can then be provided, which in particular preferably also within the vacuum chamber 4 to be ordered. According to the invention, a voltage-sensitive element for such an amplitude stabilization is therefore preferably installed within the vacuum apparatus.

The requirement for an electrical circuit within the vacuum chamber 4 means a deteriorated control over the magnetic field there, because almost all commercially available electronic components contain a diffusion barrier made of the ferromagnetic metal nickel (and the rest cause problems with the reliability and durability of soldered connections). The setting of a desired magnetic field is important for many laser spectroscopic examinations of ions or atoms and very important for the correct function, for example of a quantum computer, so that an actuator for the magnetic field is preferably provided for this, particularly preferably also within the vacuum chamber 4 ,

With the elements described, the setting of amplitude, frequency and phase or phase correctness between different control circuits is a control problem that can be solved with the methods customary for this field. What remains is the question of how to find the right guidelines for these values. In the phase this is trivial: all electrodes operated with AC voltage 10 . 20 whose common field is a ponderomotive potential and thus an ion trap 1 trained, must be operated in the correct phase, i.e. with an identical frequency and with the same or opposite phase. Another phase relationship between the electrodes regularly leads to an increased movement of the trapped ion or ions, so that, for example, reaching or reaching the lamb thickness range is made more difficult or prevented. Accordingly, the appropriate choice of the amplitudes used for the control is open.

It is common to trap individual (or more) ions by first providing the ion trap (i.e. switching on its AC voltage source) and then generating ions as close as possible to the center of the trap. Traditionally, atoms are bombarded with electrons from a miniature furnace in order to ionize them by impact ionization; meanwhile, however, it is preferred to photoionize such atoms with a laser. This has the advantage that fewer atoms are needed because photoionization is much more efficient. The preferred approach also means that electrodes and everything else that is in a vacuum is less contaminated with atomic vapor.

The ion or ions loaded into the trap have a high temperature, because their kinetic energy ideally and minimally corresponds to that with which the atoms were traveling out of the furnace, i.e. on average a temperature that is significantly higher than room temperature, which they have in the conservative ponderomotive Keep potential long if you don't cool it down. For this purpose, for example, another laser is used for so-called Doppler cooling: it is emitted from an atomic transition in the atom into the red out of tune on the ion or ions. This means that only ions that move towards the laser are in optical resonance. When a light particle (photon) is only then absorbed, they are slowed down and therefore receive less kinetic energy, on average even after they have emitted (emitted) a corresponding photon.

With the commonly used transitions in the appropriate ions, this process can be roughly 10 million times per second respectively. Due to the emission of photons, the ion can be “seen” with a suitable choice of laser detuning even when the optimal temperature for Doppler cooling has been reached. With usual experimental parameters, it roughly corresponds to 10 remaining quanta of each movement mode; it can be further reduced by tricks, including side band cooling.

“Seeing” is in quotation marks, because in some cases this may be possible, but one usually uses very sensitive detectors, often even single-photon detectors. A large number of experiments and measurements are possible with this and with suitably controlled lasers; it will still be important that there is a laser spectroscopic possibility of measuring the average number of quanta of the vibration modes of an ion, the measurement assuming that there are not too many. For the optimal cooling result mentioned, it is important that the ion feels as little of the alternating field as possible. In an ideal quadrupole field, this is automatically the case if it is at the minimum of the ponderomotive potential. However, because of the possibility (and thus practical safety) of unintended stray electrical fields, this is only the case if these are shielded or compensated by an opposing field. For this purpose, each individual ion trap preferably has additional electrodes 30 with DC electrode sections 32 which are driven with direct current (or almost direct current).

Such direct current electrodes 30 can also be used to move ions. The preferred embodiment for this is a so-called linear ion trap, cf. the description of the 4 and 5 , where the ponderomotive potential is zero not only at one point, but along a whole line (in mathematician: it disappears on this line). Then using DC electrodes 30 to ensure that it is kept at one point along this line (the Earnshaw theorem only says that this does not work in all spatial directions using DC fields). By suitable changes of this direct current control (strictly speaking only a quasi direct current control, which is characterized by a frequency which is considerably lower than the alternating current controls which generate the ponderomotive field), individual ions or even entire ion crystals can be moved.

In principle, each of the DC voltage electrode sections 32 with an independent potential. In a practical implementation, several of the DC voltage electrode sections can also be considered 32 to be acted upon with the same potential, for example by joint connection to a DC voltage supply.

Mechanical tolerances of the ion trap controlled with alternating voltage are problematic 1 forming electrodes 10 . 20 , Because even relatively small deviations can lead to a potential threshold, which is then also small on the scale of the total ion trap potential depth, but has a considerable size on the scale of the desired ion temperature that is many orders of magnitude smaller. In the worst case, it can happen that the ion is no longer locked in all directions when moving on the flank of such a potential threshold and moves ballistically in accordance with the potential energy obtained, which is generally undesirable and depending on the application, for example in quantum computers , the function can have restrictive consequences. This leads, for example, to the aforementioned scientific article by Lekitsch et al. a requirement to position adjacent ion trap modules with a precision of better than about 10 micrometers to each other, which is not practical for larger module compositions.

The individual control of individual electrodes according to the invention 10 . 20 a linear ion trap 1 in principle it allows instead of the electrodes 10 . 20 . 30 to arrange mechanically precise, to translate their actual arrangement into a suitable control. This means that they no longer have to be positioned precisely, but only have to be controlled appropriately, that is to say in particular controlled with the appropriate amplitude.

An ion, which is the AC field of the trap electrodes 10 . 20 senses more, experiences an increased heating rate. This effect is used according to the invention to obtain a measure of how much an ion feels a potential threshold of the ponderomotive potential. It will be useful to be able to select this additional heating rate (and thus the measuring range) appropriately. This is possible if a desired, additional AC voltage matching the vibration frequency of the ion is fed into the ion trap drive AC voltage.

For example, a (mostly unwanted) variation in the vibration frequency can be measured by suitably detuning the additional AC voltage from the desired vibration frequency. This must either be done in advance, or a corresponding, but spectrally broadened signal must be used as an additional feed instead of the additional AC voltage.

The bottom line is that a (repeated) measurement not only allows you to determine how much an ion is exposed to a potential threshold of the ponderomotive potential (or rather the alternating field that generates it), but also in which direction of the change in control parameter an improvement can be achieved. The amplitude of the electrodes driven with alternating current is preferably a parameter 10 . 20 to choose. This is also called a gradient descent optimization process. Almost optimal ponderomotive potentials for normal movement of ions, movement beyond ion trap module boundaries, and movement through crossing points should be achieved.

A comparable method, which is sensitive to magnetic fields, is used to compensate for magnetic fields along the movement of ions.

8th shows schematically and exemplarily an arrangement of several ion trap modules 300 in three dimensions. Each of the ion trap modules 300 can, for example, the electrode arrangement of the ion trap 1 as in 5 is shown schematically, and the electronic arrangement, as shown schematically in 7 shown correspond. The consequence of the compensation of magnetic fields along the movement of ions is that the ion trap modules also fit mechanically poorly 300 can be made electrically suitable. This enables ion trap modules 300 not just next to each other, but also at right angles or with different geometries. This does not mean the joining with which flow continues around a corner, i.e. a rotation of about 90 ° along a joining edge, but rather a rotation of about 90 ° or another value along the linear path L along which the ions can be moved.

Each of the ion trap modules 300 has, for example, the finger-like electrode structure, that is to say, for example, that the substrate material is milled away in the area shown as a comb. Each of the ion trap modules also points 300 in the schematic view electronic components 310 . 320 and 330 on, for example the resonator 100 the ion trap 1 integrate.

The entire array of ion trap modules 300 is in a vacuum, i.e. inside the vacuum chamber 4 , Optical components are in the for better visibility 8th , as in the other figures, omitted.

Finally shows 9 schematically and exemplarily a perspective view of the geometry of the linear ion trap 1 ,

A section is shown perpendicular to the linear trajectory of an ion 6 that is in the middle between your fingers 12 . 22 the opposite-pole driven AC electrodes. It is not only the cut, but also the ion trap that continues into the depth 1 shown. Through the perspective are single fingers 12 . 22 , each individually controllable electrodes 10 . 20 represent, visible. The cut is also chosen so that a ceramic substrate 50 in the top right and bottom left corner. In other words, in this example, the arrangement of the fingers 12 and 22 offset along the longitudinal direction, that is, the fingers 22 that lie in the cutting plane are shown cut through while the fingers 12 are shown in a top view.

Accordingly, it becomes an electrical circuit for driving ion traps 1 be proposed for laser spectroscopy on single ions. This applies, for example, to the areas of application of an ion trap-based optical atomic clock or an ion trap-based quantum computer. The associated circuit is essentially based on an electrical resonator, which is necessary, among other things, to suppress electrical noise (a resonator amplifies vibrations in the resonance range and suppresses all other vibrations). Without this suppression, individual ions would be exposed to an increased so-called heating rate: their (laser-cooled) vibration movement in the ion trap, which is usually technically suppressed for laser spectroscopic applications, would increase more than is technically possible without intervention.

Such an increase is usually undesirable, however, since too much such movement or even the increase itself is problematic for most (desired) laser-ion interactions. So far, different types of such resonators for ion trap drives are known, but only one variant, the “helical resonator”, is used in connection with ion traps designed for single ion operation. This is because only large copper air coils achieve the desired quality.

In contrast, according to the invention, mass-producible resonators, such as quartz crystals, ceramic filters, piezoelectric components or surface acoustic wave filters, are actually used instead of copper air coils for small signal applications. The expected accuracy in the resonance frequency enables a multitude of new applications. This includes the use of several AC voltage sources in an ion trap and the possibility of then adjusting their properties purely electrically, for example to compensate for mechanical manufacturing tolerances or to set up crossing points in the paths along which ions can be transported in some ion traps in a particularly simple and particularly high-quality way to be able to. These applications also include the possibility of connecting separate ion traps without having to guarantee extreme mechanical tolerances. This is even conceivable in an angled form, so that ion trap modules assembled in this way do not have to be limited to one level, but can be designed to fill the space, for example stacked in 3 dimensions.

The invention therefore solves the problem of providing a small, electrical circuit for the production of ion traps that can be mass-produced, noise-filtered and power-recycling through resonance, and to disclose methods for successful use.

Another object of the invention is to define the DC component of the applied AC voltage or to make it optionally adjustable without generating significant additional noise at a movement frequency of the ions.

It is a further object of the invention to make this power recycling so stable or frequency reproducible by resonance that it is possible to drive different electrodes of an ion trap with different electric drives at the same frequency with a defined and optionally also adjustable phase and amplitude ratio.

An additional object of the invention is to create a possibility of measuring the AC voltage applied to the ion trap and its time profile, for example in order to readjust its phase and / or its amplitude.

Finally, it is also an object of the invention to provide a possibility of integrating the electrical drive of an ion trap into the vacuum chamber containing the ion trap.

The invention therefore consists in the misappropriation of resonators usually used exclusively for small signal filtering, frequency stabilization, as actuators or otherwise with low voltages and currents for an application due to parasitic capacitances in or near the field of power electronics, the electrical drive of an ion trap.

A piezoelectrically contacted quartz crystal similar or identical to the frequency-determining components in quartz oscillators operated with micro signals is used as a resonator for driving an ion trap by switching it between two electrodes fed in alternating phase with alternating voltage.

At least one resonance arises, in which energy mechanically or piezoelectrically stored in the crystal is partially converted into electrostatic energy in the parasitic capacitance formed by the ion trap and vice versa. This embodiment thus fulfills the object of the invention; This ion trap drive can expediently in turn be driven by an external circuit which is, for example, capacitively coupled or connected via a capacitive voltage divider.

In order to achieve a successful excitation of the crystal, which behaves non-linearly with larger amplitudes, the frequency can be adjusted or readjusted to the currently reached amplitude.

To define or adjust the direct current component of the AC voltage thus applied to ion trap electrodes, an RC element with a very long time constant, in which the capacitance is wholly or partly shaped by the parasitic capacitance of the ion trap, is connected to the ungrounded ion trap electrode. As a result, the noise generated by the resistor can be filtered so strongly that it no longer makes a significant contribution to the movement frequency of one or more ions located in the ion trap.

In the application with independent control of two or more electrodes of the ion trap, the design described is multiplied accordingly. In the version with control integrated in the vacuum chamber, at least the resonator described is contained in this vacuum chamber.

To measure the time profile of the voltage actually applied to the ion trap electrodes, it is possible to generate a correspondingly lower voltage by means of predominantly capacitive voltage dividers. By means of a control loop, the phase and amplitude can be regulated to the desired control values.

Example 1. The use of at least one quartz crystal as a resonator to drive an ion trap, to filter drive noise, to reduce drive performance, or both, this resonator being directly or indirectly connected to one or more of the electrical capacitances or other electrical components on electrodes Ion trap is connected.

Example 2. The use of at least one ceramic resonator or ceramic filter as a resonator to drive an ion trap to filter drive noise, achieve power reduction of the drive, or both, this resonator directly or indirectly by means of one or more electrical capacities or other electrical Components is connected to electrodes of an ion trap.

Example 3. The use of at least one surface acoustic wave filter as a resonator to drive an ion trap to filter drive noise, achieve a reduction in power of the drive, or both, this resonator being directly or indirectly by means of one or more electrical capacitances or other electrical components on electrodes of one Ion trap is connected.

Example 4. The use of at least one MEMS device as a resonator to drive an ion trap to filter drive noise, achieve a reduction in power of the drive, or both, this resonator being connected directly or indirectly by means of one or more electrical capacitances or other electrical components Electrodes of an ion trap is connected.

Example 5. The use of at least one piezoelectric resonator, piezoelectric transformer, or piezoelectric resonance transformer as a resonator to drive an ion trap to filter drive noise, achieve performance degradation of the drive, or both, this resonator directly or indirectly using one or more electrical Capacities or other electrical components is connected to electrodes of an ion trap.

Example 6. The use of an RC low-pass filter with a resistance greater than one megaohm, the capacitance being eliminated or being able to be formed exclusively from parasitic capacitance, on an ion trap electrode operated with alternating voltage on a resonator, in order to obtain a desired direct voltage or a In comparison to the ion trap drive AC voltage, only slowly changing voltage should be applied as an offset to this AC drive voltage.

Example 7. The use of any low-pass filter on an ion trap electrode operated with AC voltage on a resonator in order to apply a desired DC voltage offset or a voltage which changes only slowly compared to the ion trap drive AC voltage as an offset to this AC drive voltage.

Example 8. The use of a capacitive voltage divider to measure or control the AC voltage applied to ion trap electrodes, this voltage divider being within the vacuum chamber in which the ion trap is located.

Example 9. An electrical control of a resonator which is used to drive an ion trap and whose resonance frequency is detectable, the frequency of the control of the resonance frequency being either adjusted or readjusted, even if it only determines a frequency range according to a fixed scheme without determining the instantaneous resonance frequency or vibration amplitude traverses.

Claims (31)

Ion trap (1) with at least two electrodes (10, 12, 20, 22), which are designed to generate an electric field that has an attractive ponderomotive potential in at least one area, an electrical resonator (100) and a vacuum chamber ( 4), the electrical resonator (100) being set up to supply electrodes (10, 12, 20, 22) of the ion trap (1) with an alternating voltage, and the electrical resonator (100) having an oscillating circuit (110), wherein the resonant circuit (110) is arranged within the vacuum chamber (4), characterized in that the resonator (100) selected at least one element from the list consisting of: - a quartz crystal, - a ceramic filter, - a piezoelectric component, and - has a surface acoustic wave filter. Ion trap (1) after Claim 1 , wherein the ion trap (1) is designed to keep ions of an effective temperature with at most 1 K within the vacuum chamber. Ion trap (1) according to one of the preceding claims, wherein the electrical resonator (100) is set up to supply electrodes (10, 12, 20, 22) of the ion trap (1) with an AC voltage in a frequency range between 1 MHz and 1 GHz , Ion trap (1) according to one of the preceding claims, wherein the vacuum chamber (4) is set up to an ultra-high vacuum in its interior to maintain, in particular to maintain a pressure of between 10 ^-6 mbar and 10 ^-12 mbar and particularly preferably to maintain a pressure of at most 10 ^-10 mbar. Ion trap (1) according to one of the preceding claims, wherein the ion trap (1) has a driver (120) which is set up to drive the electrical resonator (100) and is designed as a high-impedance and / or high-voltage driver. Ion trap (1) according to one of the preceding claims, wherein the electrical resonator (100) has a frequency-adjusting element. Ion trap (1) according to one of the preceding claims, further comprising a control circuit for amplitude stabilization of the voltage across electrodes (10, 12, 20, 22) of the ion trap (1), the control circuit comprising a voltage-sensitive element which is located within the vacuum chamber (4 ) is arranged. Ion trap (1) according to one of the preceding claims, wherein the drive frequency of the ion trap (1) is generated within the vacuum chamber (4). Ion trap (1) according to one of the preceding claims, wherein the resonator (100) is set up to close the electrodes (10, 12, 20, 22) of the ion trap (1) with an identical frequency and the same or opposite phase, but with a different amplitude apply. Ion trap (1) after Claim 9 The resonator (100) is set up to compensate for a geometric manufacturing deviation of the electrodes (10, 12, 20, 22) by a choice of the amplitude. Ion trap (1) according to one of the preceding claims, wherein the ion trap (1) is designed as a linear ion trap (1), such that a potential along a longitudinal axis (L) assumes a minimum over a line. Ion trap (1) after Claim 11 , which furthermore has direct current electrodes (30, 32), the direct current electrodes (30, 32) being set up, in addition to an existing ponderomotive potential, which has an attractive effect along the longitudinal axis (L), one which in this combination has an attractive effect on one point Generate potential, and in particular, by means of suitable control of the direct current electrodes (30, 32), to cause a displacement of the point along the longitudinal axis (L). Ion trap (1) after Claim 11 or 12 , wherein the ion trap (1) has two crossing linear axes, the longitudinal axis and a transverse axis, along which the potential assumes a minimum over a line and which intersect at a crossing point. Ion trap (1) according to one of the preceding claims, wherein the electrodes (10, 12, 20, 22) are designed as linear electrodes. Ion trap (1) after Claim 14 , wherein the electrodes (10, 12, 20, 22) are arranged within at least two substantially parallel layers, the area which can be used for capturing the ions being formed in a space between the outermost of the at least two layers. Ion trap (1) after Claim 15 , The opposite layers of the electrodes (10, 12, 20, 22) being designed as opposite poles of the AC voltage supply of the resonator (100). Ion trap (1) after Claim 16 The electrodes (10, 12, 20, 22) have a finger-like structure, a group of the fingers (12, 22) each being controllable independently by a resonator (100). Ion trap (1) after Claim 17 , wherein each of the groups of fingers (12, 22) comprises equally spaced fingers (12, 22), adjacent fingers (12, 22) being contained in different groups. Ion trap (1) after Claim 17 or 18 , wherein an intermediate space (14, 24) is formed between fingers (12, 22) of the finger-like structure. Ion trap (1) after Claim 19 , The intermediate space (14, 24) being at least partially, in particular entirely, metallized. Ion trap (1) according to one of the preceding claims, wherein the ion trap (1) has a modular structure, in particular a plurality of electrodes (10, 12, 20, 22) and a plurality of resonators (100) can be assembled in a modular manner. Ion trap (1) after Claim 21 , wherein adjacent modules (300) of electrodes (10, 12, 20, 22) are arranged in the same plane and / or in planes rotated by approximately 90 ° relative to one another, preferably a longitudinal axis or a transverse axis of the one module (300) corresponds to the longitudinal axis or the transverse axis of the adjacent module (300). Ion trap (1) after Claim 22 , wherein the adjacent modules (300) are designed such that ions along the longitudinal axis (L) or the Transverse axis between adjacent modules (300) are movable. Ion trap (1) according to one of the Claims 21 to 23 , The modules (300) being stackable in three dimensions. Method for calibrating an alternating voltage field of an ion trap according to one of the Claims 1 to 24 , the method comprising the following steps: - feeding in an AC voltage for driving the ion trap (1), - feeding in an additional AC voltage which is selected such that it matches a vibration frequency of an ion in the ion trap (1), - determining one increased heating rate of the ion in the ion trap (1) due to the additionally fed AC voltage. Procedure according to Claim 25 , which further comprises repeating the steps of feeding in the AC voltage, feeding in the additional AC voltage and determining the increased heating rate while changing a parameter, in particular a drive amplitude of an AC electrode. Procedure according to Claim 26 , which further comprises the following step: - calculating an approximate gradient of the heating rate with respect to the change in the parameter by means of the determined heating rates. Procedure according to Claim 27 , which further comprises repeating the steps of feeding in the AC voltage, feeding in the additional AC voltage, determining the increased heating rate and calculating the approximate gradient of the heating rate while iteratively changing the parameter in order to find a target value of the parameter, the calculated gradient in particular Heating rate is minimized. Use of a quartz crystal, a ceramic filter, a piezoelectric component, and / or a surface wave filter as an electrical resonator (100) for driving an ion trap (1). Use after Claim 29 , wherein the resonator (100) is connected directly or indirectly to electrodes (10, 12, 20, 22) of the ion trap (1). Use after Claim 30 The resonator (100) is connected to electrodes (10, 12, 20, 22) of the ion trap (1) by means of one or more electrical capacitances and / or further electronic components.

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