CN220173211U - Impedance matching parametric amplifier, component and quantum computer - Google Patents

Abstract

The utility model discloses an impedance matching parametric amplifier, an impedance matching parametric amplifier component and a quantum computer, and belongs to the field of quantum computing technology manufacturing. The impedance matching parametric amplifier includes an amplifying circuit integrated into a substrate. The amplifying circuit includes: josephson parametric amplifier, circulator and reflective impedance transformer. The two ends of the reflective impedance transformer are respectively connected with the Josephson parametric amplifier and the circulator. The impedance matching parametric amplifier has higher integration level by integrating the components in the substrate, reduces complex circuits among various discrete devices and independent equipment and the impedance adaptation problem caused by the complex circuits, and can also reduce noise.

Description

Impedance matching parametric amplifier, component and quantum computer

Technical Field

The utility model belongs to the field of quantum information, in particular to the field of quantum computing technology manufacturing, and particularly relates to an impedance matching parametric amplifier, an impedance matching parametric component and a quantum computer.

Background

In superconducting quantum systems, signals output by a quantum processor are collected and analyzed in order to obtain the result of quantum computation. However, the general output signal is very weak, so that it is selected to superimpose a multi-stage amplifier on the output line of the signal in order to increase the signal strength. The amplifier may be implemented as a quantum parametric amplifier; which is a parametric amplifier with near quantum-limited noise.

The amplifying of the output signal of the quantum processor is realized, the quantum parametric amplifier is required to realize the main signal amplifying function, and other independent components are required to complete the functions of signal transmission, signal isolation and the like. Therefore, the connection between the independent components can generate serious impedance mismatch, thereby affecting the performance of the quantum parametric amplifier, generating the phenomenon of jitter of gain, and causing the phenomena of center frequency point offset, insufficient gain bandwidth and the like when serious. And these components have a large volume occupation, so that space availability in a support system of the superconducting quantum chip, such as a cooling system, is reduced.

Disclosure of Invention

Examples of the present utility model provide an impedance matching parametric amplifier, components, and quantum computers. The scheme can reduce the complexity of equipment line configuration in the superconducting quantum computer, reduce space occupation and have stronger anti-interference performance.

The exemplary embodiment of the present utility model is implemented as follows.

In a first aspect, examples of the present utility model provide an impedance-matched parametric amplifier. Which includes an amplifying circuit integrated into a substrate. The amplifying circuit includes:

a Josephson parametric amplifier coupled to a control circuit for inputting the pump signal;

a circulator having a loop including a josephson junction, the loop defining a first port for receiving a signal to be amplified, a second port and a third port for receiving a target signal formed by amplification and input from the second port; and

a reflective impedance transformer has one end connected to the josephson parametric amplifier and the other end coupled to the second port of the circulator.

According to some examples of the utility model, a josephson parametric amplifier comprises: a first circuit and a second circuit having a common terminal through which the Josephson parametric amplifier is connected to the reflective impedance transformer;

wherein the first circuit comprises a capacitor having one end connected to ground and the second circuit comprises a device providing a nonlinear inductance having a josephson junction having one end connected to ground.

According to some examples of the utility model, the device providing the nonlinear inductance has at least two josephson junctions;

alternatively, the device providing the nonlinear inductance is a superconducting quantum interferometer circuit;

alternatively, the device providing the nonlinear inductance has at least one ring-shaped sub-circuit, at least one sub-circuit containing more than two josephson junctions;

alternatively, the means for providing a nonlinear inductance comprises a josephson junction in a ring sub-circuit, the control circuit being further configured to input a bias signal to change the inductance value of the means for providing a nonlinear inductance.

According to some examples of the utility model, the circulator has three josephson junctions, and the josephson junctions are arranged in the ring circuit alternately with the first port, the second port and the third port.

According to some examples of the utility model, the first port, the second port, and the third port are each capacitively coupled to an independent drive circuit, the first port being capacitively coupled to an independent signal circuit, and the third port being a signal output.

According to some examples of the utility model, the impedance matching parametric amplifier further comprises: an isolator integrated onto the substrate, the isolator connected to the third port to prevent the back stage signal from reflecting back to the front stage.

According to some examples of the utility model, the isolator is a josephson junction based isolator;

alternatively, the number of the separators is at least two, and all the separators are connected in series;

alternatively, the isolator includes a parallel circuit having one end grounded and the other end connected to the third port of the circulator, the parallel circuit including a capacitor and a superconducting quantum interferometer connected in parallel, and the superconducting quantum interferometer is controllably coupled with the operating circuit by a magnetic field.

In a second aspect, examples of the present utility model provide an impedance matching parametric amplifier assembly comprising a plurality of impedance matching parametric amplifiers; the impedance matching parametric amplifiers are commonly connected to the signal output line through a microwave switch.

According to some examples of the utility model, the impedance matching parametric amplifier assembly further comprises a low noise amplifier configured independently of the substrate, the signal output line being connected to the low noise amplifier.

In a third aspect, examples of the utility model provide a quantum computer comprising the aforementioned impedance matching parametric amplifier, or impedance matching parametric amplifier assembly.

The beneficial effects are that:

existing parametric amplifiers are typically assembled from various discrete devices and equipment connected by wires such as coaxial cables. However, such amplifiers are bulky and thus occupy more refrigerator space when applied to superconducting quantum computers for reading qubits. Also, the use of various lines makes impedance matching difficult, and is susceptible to generation and adverse effects of noise.

While the impedance matching parametric amplifier in the examples of the present utility model can significantly reduce its volume, as well as space occupation, by integrating the amplifying circuit into the substrate. In addition, since each structure is integrated into the substrate, the connection between each structure is also integrated into the substrate accordingly. In this way, the circuit can be designed and manufactured according to the actual impedance matching requirement, so that the quality and the consistency and the matching performance of the impedance design are higher. And the on-chip integration of the structures can be more beneficial to electromagnetic characteristic design so as to improve noise resistance.

Drawings

For a clearer description, the drawings that are required to be used in the description will be briefly introduced below.

Fig. 1 is a schematic block diagram of a josephson parametric amplifier in an example of the utility model;

fig. 2 is a schematic block diagram illustrating an example circulator constructed based on three josephson junctions according to the utility model;

FIG. 3 is a schematic block diagram of the circulator of FIG. 2 connected to corresponding signal and drive circuits;

FIG. 4 is a schematic block diagram of an impedance matching parametric amplifier in an example of the utility model;

FIG. 5 is a schematic block diagram of another impedance matching parametric amplifier in an example of the utility model;

FIG. 6 is a schematic block diagram of an impedance matching parametric amplifier assembly in accordance with an example of the present utility model;

fig. 7 is a schematic block diagram of another impedance matching parametric amplifier assembly in an example of the utility model.

Reference numerals illustrate: 100-Josephson parametric amplifier; 101-common terminal; 102-a first circuit; 1021-a capacitor; 103-a second circuit; 1031-Josephson junction; 104-a control circuit; 200-circulator; 201-a driving circuit; 202-a signal circuit; 300-reflective impedance transformer.

Detailed Description

Since superconducting qubits have strong sensitivity to noise, they are very susceptible to various kinds of noise. While quantum computation requires various control operations on the qubits, and reading operations are required to obtain the result of quantum computation. Then these operations may have an unexpected effect on the qubit.

In particular, the signal obtained when a read operation is performed is very weak, and thus amplified for valuable interpretation. While some current amplifiers in microwave devices introduce noise while amplifying the signal, making interpretation of the actual read acquisition signal difficult to achieve. With this premise, a parametric amplifier is applied. The parametric amplifier is capable of satisfying the measurement of weak microwave signals near the quantum limit.

Currently, superconducting quantum chips are configured to operate in dilution refrigerators. While the space of the dilution refrigerator and the refrigeration power are limited and valuable. And the number of various operation lines and components required to be used in consideration of the qubit is also generally large. The performance of a quantum chip that can be achieved is greatly limited if the parametric amplifier occupies too much limited space. While considering that the stability of connection of various lines inside the parametric amplifier, impedance characteristics, etc. may make its actual use value lower than expected.

In view of the above-described practical situation, in the example of the present utility model, the inventors have proposed a solution, thereby largely solving the problems of the current parametric amplifier. By this solution, high integration of the parametric amplifier can be achieved, and problems such as stability, impedance characteristics of connection lines between internal components being difficult to match to design requirements, and the like can also be reduced. In particular, the solution is an on-chip integrated parametric amplifier, and therefore has a more optimal space utilization, so that the space occupation can be significantly reduced.

In an exemplary solution, the inventors have coupled the josephson parametric amplifier to the circulator via a reflective impedance matching structure. The signal to be amplified is thus fed through the circulator and the pump signal is fed through the josephson parametric amplifier, so that the signal is amplified and the amplified target signal is then fed through the circulator.

Illustratively, in some examples, the inventors propose an impedance matching parametric amplifier. And in particular, the impedance matching parametric amplifier is integrated, various components are integrated into a substrate, so that the overall size of the impedance matching parametric amplifier is smaller, the matching degree among the components is high, the impedance matching parametric amplifier can be designed in advance according to requirements and can be better matched with design targets after being manufactured, and meanwhile, the impedance matching parametric amplifier can be better prevented from being negatively influenced by the environment.

In an example, the impedance matching parametric amplifier mainly includes an amplifying circuit integrated onto a substrate. And the amplifying circuit comprises a josephson parametric amplifier, a circulator and a reflective impedance transformer as described above.

As the name implies, the josephson parametric amplifier (Josephson Parametric Amplifier, JPA) is constructed based on josephson junctions. A large amount of macroscopic freedom degrees can be frozen in a superconducting state, so that the introduction of extra noise can be avoided, and the amplification of signals can be realized perfectly. In a Josephson parametric amplifier, a nonlinear LC resonant circuit is provided using a Josephson junction and a capacitor. Wherein the josephson junction can act as an equivalent nonlinear inductance.

When amplifying, the pump energy can cause the circuit to be driven into a nonlinear operating region by periodically modulating the equivalent nonlinear inductance therein. And when the frequency (omega _p ) At the proper frequency and amplitude, parametric amplification converts energy into input signal, and accompaniment signal energy such as various idlers. In general, the amplification operation can be performed when the frequency of the pump signal is equal to the frequency of the signal to be amplified. In some examples, three-wave mixing amplification, or four-wave mixing amplification, may be implemented by appropriate design. Correspondingly, in the three-wave mixing amplification mode, the frequency of the input pump signal may be selected to be equal to the frequency of the signal to be amplified. Similarly, in the four-wave mixing amplification mode, the frequency of the input pump signal may be selected to be equal to twice the frequency of the signal to be amplified.

Such a josephson parametric amplifier has low losses and its parameters are easy to design and characterize, while also having good gain and amplification effects that can approach the quantum noise limiting performance.

In an alternative example, the josephson parametric amplifier comprises a structure in which a josephson junction (i.e. a single junction) and a capacitor are connected in parallel. Alternatively, in other examples, the josephson parametric amplifier may also comprise a parallel arrangement of a superconducting quantum interferometer (Superconducting Quantum Interference Device, SQUID) and a capacitor. The SQUID may be: is a direct current superconducting quantum interferometer with two josephson junctions, i.e. a DC-SQUID.

In general, as shown in fig. 1, in the example of the utility model, the josephson parametric amplifier 100 comprises: a first circuit 102 and a second circuit 103 having a common terminal 101 and the josephson parametric amplifier 100 is connected to the reflective impedance transformer 300 via the common terminal 101. Wherein the first circuit 102 comprises a capacitor 1021 with one end grounded and the second circuit 103 comprises a device providing a nonlinear inductance having a josephson junction 1031 with one end grounded.

In different examples, different configurations may be made as needed to implement different configurations of josephson parametric amplifier 100. The device therein providing the nonlinear inductance may have one or more josephson junctions 1031. In the example of a device providing non-linear inductance with at least two josephson junctions 1031, two or more of the josephson junctions 1031 may be in-loop, while the other one or more josephson junctions 1031 may alternatively be arranged in non-loops. Thus, the device that in some cases provides nonlinear inductance is a superconducting quantum interferometer circuit; i.e. two parallel josephson junctions 1031 in the loop.

Similarly, in other examples, the device providing the nonlinear inductance has at least one ring-shaped sub-circuit, and at least one sub-circuit contains more than two josephson junctions 1031. It is noted that when there is only one josephson junction 1031 in one ring-shaped sub-circuit, shorting of the two electrodes of the josephson junction 1031 is avoided.

For the example of a device providing non-linear inductance in the form of a plurality of josephson junctions 1031 in the loop (e.g. squid), the control circuit 104 for inputting the pumping signal may also be configured to be able to input a bias signal (which may provide a bias current, e.g. by a voltage source or the like) to change the inductance value of the device providing non-linear inductance. Thus, the control circuit 104 may implement a combination of dc bias and rf pump signals and be coupled into a device that provides nonlinear inductance. Wherein the combination of the dc Bias and the rf pump signal can be realized by a Bias-Tee. Bias-Tee is a three-terminal network that can configure dc Bias points without interfering with other devices. The bias can combine signals from different lines or devices-direct current signals and microwave signals.

In the example of enabling transmission of the combined bias signal and pump signal by the control circuit 104, by co-intentional selection of the bias signal and pump signal, it is possible to achieve a readily distinguishable frequency separation between the actually desired target signal and other normally unwanted interfering signals in the amplified signal-e.g. a spectral separation with different signals being able to be split by filters-so that the amplified obtained target signal can be extracted more conveniently.

This is to take into account that in the three-wave mixing amplification mode as mentioned above, the pump signal has the same frequency as the signal to be amplified, so that the amplified target signal is not easily separated from the pump signal and thus the amplified target signal is difficult to extract.

In the foregoing, the circulator (or circulator) in the exemplary impedance-matched parametric amplifier is capable of unidirectionally transmitting high frequency signal energy. The device can sequentially transmit the incident signals entering any port into the next port according to the determined direction; and is typically a multiport device. In the illustration of the present utility model, circulator 200 is also a multiport device and is a three port device. In other examples, the circulator 200 may also be a four-port device, or a more-port device (which may be implemented by cascading multiple circulators 200).

Based on the application reality (milli-kelvin) in superconducting quantum systems and in some examples of the utility model integrated into the substrate, construction of circulator 200 based on josephson junctions 1031 may be chosen. For example, in the illustrated circulator 200, the circulator 200 has three josephson junctions 1031. And, the josephson junction 1031 is arranged in the ring circuit alternating with the first port, the second port and the third port; referring to fig. 2, two josephson junctions 1031 (intersecting portions in fig. 2) that are sequentially adjacent on the loop define a port.

Wherein the circulator 200 has a loop with a josephson junction 1031 and in which a first port, a second port and a third port are defined. The first port can receive a signal to be amplified, and the signal to be amplified is output to the JPA from the second port. In which the target signal is amplified by energy gained by the excitation of the pump signal. The target signal is reflected into the second port and then into the third port. That is, the third port can accept the target signal amplified and input from the second port.

To facilitate the use of, for example, signal input and driving of the circulator 200, the first port, the second port and the third port are each capacitively coupled to a separate driving circuit 201 (which may be used to input a bias voltage, which is used in the operating condition of the circulator 200), and the first port is capacitively coupled to a separate signal circuit 202, which is used as a signal output. The signal circuit 202 is used for implementing corresponding signal transmission, and the driving circuit 201 can provide the working condition of the circulator 200. In fig. 3, a signal circuit 202 and a drive circuit 201 coupled to a port of a circulator 200 by means of capacitive coupling are depicted; and the signal circuit 202 and the drive circuit 201 in one port are labeled as an example. It should be noted that the second port of the circulator 200 is connected to the JPA through the reflective impedance transformer 300. Accordingly, the signal circuit 202 corresponding to the second port may be provided by a transmission line connecting the second port and the reflective impedance transformer 300.

In the impedance matching parametric amplifier, the reflective impedance transformer 300 is also provided. And has one end connected to josephson parametric amplifier 100 (via common terminal 101 as described above) and the other end coupled to the second port of circulator 200, for example by capacitive coupling to a signal line of the second port. As an example, the reflective impedance transformer 300 includes Klopfenstein impedance transformation lines, or may also be in the form of λ/4 wavelength and λ/2 wavelength impedance transformation lines, or directly using λ/4 wavelength impedance transformation lines, or an impedance transformation structure made up by discrete devices. In general, the reflective impedance transformer 300 may also be a reflective resonant cavity and is, for example, selected to be implemented using coplanar waveguide transmission lines.

The impedance matching parametric amplifier based on the above described example can be disclosed by the structure shown in fig. 4; and, each input-output signal and each bias configuration therein are given. And in the example josephson parametric amplifier 100 is coupled with a control circuit 104 which inputs the pump signals.

Therefore, as a whole, a reflective impedance matching parametric amplifier (Impedance Matched Parametric Amplifier, abbreviated as IMPA) can be constituted mainly by matching the JPA with the reflective impedance transformer 300.

Based on the structure of fig. 4, it is considered that the amplified output signal may be reflected due to the impedance matching problem in the process of transmitting to the subsequent stage, and thus the signal of the previous stage may be affected. Thus, further, the configuration of the isolator may be selected. The number of spacers is not particularly limited, and one spacer may be generally selected. When a plurality of, e.g., at least two, separators are selected to be disposed, all of the separators may be mated in series.

As an integrated use, the spacers in some examples may also be integrated onto the substrate.

Depending on the manner in which it is used, the isolator is connected to the third port and can thus be used to prevent the back stage signal from reflecting back to the front stage; i.e. the isolator has the function of making the signal conduct unidirectionally, preventing the interference of signal reflection.

In the example of the utility model, based on the low temperature environment operating on superconducting qubits, it is also possible to choose to have the isolator built based on josephson junctions, and this also facilitates integration in the substrate.

As a specific and alternative example, the isolator includes a parallel circuit with one end grounded and the other end connected to the third port of the circulator 200. The parallel circuit includes a capacitor 1021 and a superconducting quantum interferometer in parallel. And the superconducting quantum interferometer is controllably coupled with an operating circuit by a magnetic field. In the circuit shown in fig. 5, the isolator includes two of the aforementioned parallel circuits connected in the output line.

Since the josephson junction 1031 (used in the form of a superconducting quantum interferometer) is used in the isolator in fig. 5, it can be fabricated in the same process as the JPA constructed by using the superconducting quantum interferometer structure. And with this form of isolator can be achieved non-reciprocal transmission with phase dependence of the radio frequency modulation of the SQUID, such as the radio frequency signal (provided by the operating circuitry).

In addition, a matching circuit is also provided in the output circuit in order to optimize the circuit. Which can act as an admittance converter to form a waveguide of a specific length (determined by the operating frequency) in the circuit. The number of matching circuits is typically chosen in dependence on the number of parallel circuits in the isolator, more specifically superconducting quantum interferometers in the parallel circuits. For example, the number of superconducting quantum interferometers therein corresponds to the number of poles. Therefore, in the two-pole isolation, two groups of superconducting quantum interferometers and three groups of matching circuits are selected; if the three-pole isolation is adopted, three groups of superconducting quantum interferometers and four groups of matching circuits are selected. In fig. 5, two-pole isolation is designed, thus having three matching circuits, and corresponding two superconducting quantum interferometers.

Since amplification of multiple signals is typically involved in superconducting quantum computing systems, it may be desirable in some examples to configure multiple amplifiers. Accordingly, an impedance matching parametric amplifier assembly is also disclosed in the examples that includes a plurality of impedance matching parametric amplifiers. The impedance matching parametric amplifiers are commonly connected with a signal output line through a microwave switch; as shown in fig. 6.

Further, each impedance matching parametric amplifier component may also be configured with a low noise amplifier. Or, the amplifiers share one low noise amplifier through equipment such as a microwave switch and the like; i.e. a multiplexed low noise amplifier, such as shown in fig. 7. The low noise amplifier may be further configured to a substrate, and connected to a low noise amplifier (Low Noise Amplifier, simply referred to as LNA) through a signal output line.

Wherein each impedance matching parametric amplifier is identified by a dashed box. Each impedance matching parametric amplifier has an independent signal input path and each has a corresponding control circuit 104 for inputting a pump signal. And corresponding ports of the respective circulators 200 may share the drive circuit 201. Since each circulator 200 has three ports, there may be three signal sources of the driving circuit 201 in this configuration.

Furthermore, it is known that by using the aforementioned impedance matching parametric amplifier or components thereof (which may be part of a reading system or component) in a quantum computer or other quantum computing system, in particular in a superconducting quantum system, the volume of the relevant device, the system, and the signal-to-noise ratio of the signal during signal transmission can be effectively controlled.

The embodiments described above by referring to the drawings are exemplary only for explaining the present utility model and are not to be construed as limiting the present utility model.

For purposes of clarity, technical solutions, and advantages of embodiments of the present utility model, one or more embodiments have been described above with reference to the accompanying drawings. Wherein like reference numerals are used to refer to like elements throughout. In the description above, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that one or more embodiments may be practiced without these specific details, and that such embodiments may be incorporated by reference herein without departing from the scope of the claims.

It should be noted that the terms "first," "second," and the like in the description and the claims of the present utility model and the above figures are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order. It is to be understood that the data so used may be interchanged where appropriate such that the embodiments of the utility model described herein may be implemented in sequences other than those illustrated or otherwise described herein. Furthermore, the terms "comprises," "comprising," and "having," and any variations thereof, are intended to cover a non-exclusive inclusion, such that a process, method, system, article, or apparatus that comprises a list of steps or elements is not necessarily limited to those steps or elements expressly listed but may include other steps or elements not expressly listed or inherent to such process, method, article, or apparatus.

While the foregoing is directed to embodiments of the present utility model, other and further embodiments of the utility model may be devised without departing from the basic scope thereof, and the scope thereof is determined by the claims that follow.

Claims (10)

1. An impedance-matched parametric amplifier comprising an amplification circuit integrated into a substrate, the amplification circuit comprising:

a Josephson parametric amplifier coupled to a control circuit for inputting the pump signal;

a circulator having a loop including a josephson junction, the loop defining a first port for receiving a signal to be amplified, and a second port and a third port for receiving a target signal formed by amplification and input from the second port; and

a reflective impedance transformer has one end connected to the josephson parametric amplifier and the other end coupled to the second port of the circulator.

2. The impedance-matched parametric amplifier of claim 1, wherein the josephson parametric amplifier comprises: a first circuit and a second circuit having a common terminal through which the josephson parametric amplifier is connected to the reflective impedance transformer;

wherein the first circuit comprises a capacitor with one end grounded and the second circuit comprises a device providing a nonlinear inductance having a josephson junction with one end grounded.

3. The impedance-matched parametric amplifier of claim 2, wherein the means for providing a nonlinear inductance has at least two josephson junctions;

alternatively, the device providing the nonlinear inductance is a superconducting quantum interferometer circuit;

alternatively, the device providing the nonlinear inductance has at least one ring-shaped sub-circuit, at least one sub-circuit containing more than two josephson junctions;

alternatively, the device providing the nonlinear inductance comprises a josephson junction in a ring-shaped sub-circuit, the control circuit being further configured to input a bias signal to change the inductance value of the device providing the nonlinear inductance.

4. The impedance matching parametric amplifier of claim 1, wherein the circulator has three josephson junctions and the josephson junctions are arranged in the ring circuit alternating with the first port, the second port and the third port.

5. The impedance matching parametric amplifier of claim 4, wherein the first port, the second port, and the third port are each capacitively coupled to separate driver circuits, the first port being capacitively coupled to separate signal circuits, and the third port being a signal output.

6. The impedance-matched parametric amplifier of claim 1, wherein the impedance-matched parametric amplifier further comprises: an isolator integrated onto the substrate, the isolator connected to the third port to prevent the back stage signal from reflecting back to the front stage.

7. The impedance-matched parametric amplifier of claim 6, wherein the isolator is a josephson junction-based isolator;

alternatively, the number of the separators is at least two, and all the separators are connected in series;

alternatively, the isolator includes a parallel circuit having one end grounded and the other end connected to the third port of the circulator, the parallel circuit including a capacitor and a superconducting quantum interferometer connected in parallel, and the superconducting quantum interferometer is controllably coupled with the operating circuit by a magnetic field.

8. An impedance matching parametric amplifier assembly comprising a plurality of impedance matching parametric amplifiers as claimed in any one of claims 1 to 7;

the impedance matching parametric amplifiers are commonly connected with a signal output line through a microwave switch.

9. The impedance matching parametric amplifier assembly of claim 8, further comprising a low noise amplifier configured independently of the substrate, the signal output line being connected to the low noise amplifier.

10. A quantum computer comprising an impedance matching parametric amplifier according to any one of claims 1 to 7, or an impedance matching parametric amplifier assembly according to claim 8 or 9.