JP3970781B2 - Quantum information processing method and quantum information processing apparatus - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a quantum information processing device that represents a quantum bit by a quantum state of a physical system that resonates with a common resonator mode in an optical resonator, and in particular, reads a quantum state operation and its result in an optical resonator. The present invention relates to a quantum information processing method and a quantum information processing apparatus that facilitate the coexistence with photon detection.
[0002]
[Prior art]
In a quantum information processing device (quantum computer) that represents information in the quantum state of the physical system and performs information processing by manipulating the quantum state, the physical system representing the information (quantum bit) is set to the initial state at the beginning of the operation. There must be. Note that the term “quantum bit” may refer to quantum information itself or a physical system that carries quantum information. In the following, we will use this "qubit" representation for both meanings if it can be judged from the context and is not confusing.
[0003]
In addition, in the operation of a quantum computer, it is necessary to introduce interaction between qubits in a well-controlled manner so that information can be exchanged between qubits. Further, after the operation is completed, in order to know the operation result, the qubit must be read (observed).
[0004]
A method has been proposed in which these operations are performed using a laser capable of precise control, and an interaction between qubits is introduced by resonance of each qubit into a common resonator mode. In particular, a frequency domain quantum computer (see Non-Patent Document 1) that makes use of the difference in resonance frequency that each qubit inherently distinguishes between qubits requires difficult fine processing and delicate position control. In addition, it has the feature of good consistency with optical information processing technology.
[0005]
In such a quantum computer that couples physical systems that carry qubits in the mode of an optical resonator, a high-performance resonator with a long resonator lifetime, that is, a long photon stays in the resonator, is assembled, and a qubit is included in the resonator. Holds the physical system responsible for the quantum operation. In a high performance resonator, a resonator mode photon generated in the resonator is kept in the resonator for a long time by a reflecting mirror having a very high reflectance.
[0006]
When the result is read after the operation of the quantum operation is completed, a method using light is desirable because it has high sensitivity and can reduce noise. In that case, it would be more desirable if a technique of a frequency domain quantum computer that reads out each quantum state by distinguishing each qubit by its resonance frequency can be used.
[0007]
In the frequency domain quantum computer, a physical system having three energy states obtained by degenerating two energy states as qubits is used. Among these three states, they are called | 1>, | 2>, and | 3> in order from the lowest energy. When the result of the operation is read, the qubit (information) to be read is represented by whether the qubit (physical system) is in | 1> or | 2>. Here, the transition probability of the transition between | 1>-| 3> and the transition between | 2>-| 3> is large, and the transition probability of the transition between | 1>-| 2> is small. The transition energy between | 2>-| 3> has the same value in multiple qubits and resonates with a common resonator mode, whereas the transition between | 1>-| 3> is different in each qubit Suppose that it has a value.
[0008]
Here, light that resonates with the | 1>-| 3> transition of a desired qubit whose quantum state is desired is irradiated. Then, if the qubit is in the state of | 1>, it selectively absorbs light and passes through the state of | 3> to resonate photons having transition energy of transition between | 2>-| 3>. Discharge to vessel mode. If it is in the state | 2>, nothing happens. Therefore, if the photon can be detected when this photon emission occurs, the quantum state of the qubit can be known.
[0009]
However, since the optical resonator has a long resonator life, the emitted photons hardly come out of the resonator. In the meantime, the photon exits from the resonator in an unexpected direction due to scattering due to slight unevenness on the surface of the reflecting mirror, scattering due to the medium inside the resonator, and the like. As described above, the timing and direction in which the photons emerge from the resonator are not fixed, and there is a problem that it is difficult to detect the photons with high efficiency, and a method for efficiently reading the result of the quantum operation has not been known.
[0010]
[Non-Patent Document 1]
K. Ichimura, Opt. Commun. 196, 119 (2001).
[0011]
[Problems to be solved by the invention]
The present invention has been made in consideration of the above circumstances, and its purpose is to perform quantum computation using an optical resonator suitable for quantum information processing in which quantum bits are coupled in a resonator mode of an optical resonator. It is an object to provide a quantum information processing method and a quantum information processing apparatus that can perform result reading by using light of high efficiency.
[0012]
[Means for Solving the Problems]
In order to solve the above problems, a first aspect of the present invention is to provide a physical system including atoms, ions, or molecules dispersed in a solid crystal between a first reflecting mirror and a first end of a first optical fiber. An optical resonator in which one of the resonator modes resonates with the transition energy of the physical system between the first reflector and the second reflector located at the second end of the first optical fiber. , Irradiating the physical system with light from outside the optical resonator, manipulating the quantum state of the physical system, and after finishing the manipulation process, the first end and the second end of the first optical fiber The first end of the optical fiber is changed, the first end of the second optical fiber is moved to a position where the physical system is sandwiched between the first reflecting mirror, and light is transmitted to the physical system after the moving step. Irradiate and release photons emitted from the physical system from the first end of the second optical fiber to the second Quantum information comprising: a step of detecting by a photodetector incorporated in an optical fiber and coupled to a second optical fiber; and a step of determining a quantum state of a physical system based on the presence or absence of a photon detected in the detection step A processing method is provided.
[0013]
In the first aspect of the present invention, the first end of the third optical fiber is held at a position where the physical system is sandwiched between the first reflecting mirror and the third optical fiber from the second end of the third optical fiber. The physical system can also be illuminated through the first end of the third optical fiber.
[0014]
In the first aspect of the present invention, the resonator length of the optical resonator can be changed by changing the distance between the physical system and the first end of the first optical fiber.
[0015]
In order to solve the above-described problem, the second aspect of the present invention provides a first physical system including atoms, ions, or molecules dispersed in a solid crystal as a first reflecting mirror and a first end of a first optical fiber. A second physical system containing atoms, ions or molecules dispersed in the solid crystal is positioned between the second reflector and the second end of the first optical fiber, Forming an optical resonator in which one of the resonator modes resonates with the transition energy of the physical system between the reflecting mirror and the second reflecting mirror; and from the outside of the optical resonator, the first or second Irradiating the physical system with light to manipulate the quantum state, and after finishing the manipulation process, the first end of the second optical fiber is changed to the first end or the second end of the first optical fiber, A first or second object between the first end of the two optical fibers and the first or second reflector After the step of moving to a position sandwiching the system and the step of moving, the first physical system is irradiated with light, and photons emitted from the physical system are transferred from the first end of the second optical fiber to the second optical fiber. And a step of detecting by a photodetector coupled to the second optical fiber and a step of determining the quantum state of the first or second physical system based on the presence or absence of a photon detected in the detection step. A quantum information processing method is provided.
[0016]
In the second aspect of the present invention, the solid crystal in which the first and second physical systems are dispersed may be an integral solid crystal such as a single thin film or plate, or may be a separate solid crystal. Further, the first and second reflecting mirrors may be used in different parts of the integrated reflecting mirror, or may be separate reflecting mirrors.
[0017]
In order to solve the above-described problem, a third aspect of the present invention provides a physical system including atoms, ions, or molecules dispersed in a solid crystal between a first reflecting mirror and a first end of a first optical fiber. Of the resonator mode between the first reflecting mirror and the second reflecting mirror using a second reflecting mirror positioned and facing the second end of the first optical fiber via the acousto-optic element. One is the process of forming an optical resonator that resonates with the transition energy of the physical system, and the quantum state of the physical system by irradiating the physical system with light from outside the optical resonator without applying radio waves to the acoustooptic device , Irradiating light to the physical system to emit photons from the physical system, deflecting the traveling direction of the photons emitted by the acoustooptic device to which the radio wave is applied, and the photons deflected by the deflection process And a step of detecting presence or absence To provide a child information processing method.
[0018]
In order to solve the above problems, a fourth aspect of the present invention includes a plate-like or thin-film solid crystal including a physical system containing atoms, ions, or molecules, and having a first reflecting mirror formed on one side thereof, A physical system between a first optical fiber having a first end on the solid crystal side and a second end and a second end of the first optical fiber, and the first reflecting mirror via the first optical fiber. A second reflecting mirror capable of forming an optical resonator having an optical resonator mode that resonates with the transition energy of the first, a first end on the solid crystal side, and a second end connected to the photodetector. Irradiates light from outside the optical resonator, light irradiation means that can manipulate the quantum state of the physical system, and irradiates light to the physical system whose quantum state has changed, and emits photons from the physical system Measuring means that can be adapted, a first end of the first optical fiber and a second optical fiber. The support that can be moved in parallel with the surface opposite to the surface opposite to the surface on which the first reflecting mirror of the solid crystal is provided, and the operation of the light irradiation means Sometimes the support is held in the first position so that the first end of the first optical fiber is sandwiched between the first reflector and the first reflector, and the first of the second optical fiber is in operation when the measuring means is in operation. A support moving unit capable of holding the support in the second position so that the end sandwiches the physical system between the first reflecting mirror and the support and moving the support between the first and second positions; A quantum information processing apparatus is provided.
[0019]
In the fourth aspect of the present invention, the support further comprises a third optical fiber having a first end and a second end on the solid crystal side, and a light source connected to the second end of the third optical fiber. The first end of the first optical fiber, the first end of the second optical fiber, and the first end of the third optical fiber are opposed to the surface opposite to the surface provided with the first reflecting mirror made of solid crystal, The support moving unit can move in parallel with the opposite surface, and the first moving end of the third optical fiber is not connected to the first end when irradiating the physical system with light from the light source via the third optical fiber. The support can be positioned so that the physical system is sandwiched between the reflector and the reflector.
[0020]
In the fourth aspect of the present invention, the support moving unit may change the distance between the physical system and the first end of the first optical fiber via the support.
[0021]
In order to solve the above-described problems, a fifth aspect of the present invention includes a plate-like or thin-film-like first containing a first physical system containing atoms, ions, or molecules, and having a first reflecting mirror formed on one side. A plate-like or thin-film-like second solid crystal including a first solid crystal and a second physical system containing atoms, ions, or molecules, and having a second reflecting mirror formed on one side thereof; A first end on the physical system side and a second end on the second physical system side, and resonates with transition energy of the first and second physical systems between the first and second reflectors A second optical fiber having a first optical fiber capable of forming an optical resonator having an optical resonator mode, a first end on the first solid crystal side, and a second end connected to the first photodetector. A third optical fiber comprising: a first end on the second solid crystal side; and a second end connected to the second photodetector Irradiating light from the outside of the optical resonator to irradiate light to the first or second physical system in which the quantum state has changed, and light irradiation means capable of operating the quantum state of the first or second physical system Then, a first set of measuring means capable of emitting photons from the first or second physical system, and a first end of the first optical fiber and a first end of the second optical fiber, The solid crystal can be moved parallel to the surface opposite to the surface opposite to the surface on which the first reflecting mirror is provided, or the second end of the first optical fiber and the first The second set of the first ends of the three optical fibers is opposed to the surface opposite to the surface on which the second reflecting mirror of the second solid crystal is provided, and the surface on the opposite side of the second solid crystal And the first end of the first optical fiber is in front when the light irradiating means is in operation. A support so that the first physical system is sandwiched between the first reflecting mirror and the second physical system is sandwiched between the second end of the first optical fiber and the second reflecting mirror. Is held in the first position, and when the measuring means is operated, the first physical system is sandwiched between the first end of the second optical fiber and the first reflecting mirror, or the third optical fiber is A support capable of holding the support in the second position so that one end sandwiches the second physical system between the second reflector and the support, and the support can be moved between the first and second positions. Provided is a quantum information processing device comprising a body moving unit.
[0022]
In the fifth aspect of the present invention, the first and second solid crystals may be composed of the same body or different solid crystals. In addition, the first reflecting mirror and the second reflecting mirror can be formed of the same reflecting mirror, or can be separate reflecting mirrors.
[0023]
In order to solve the above problems, a sixth aspect of the present invention includes a plate-like or thin-film solid crystal that includes a physical system including atoms, ions, or molecules, and has a first reflecting mirror formed on one side thereof. Provided in the vicinity of a first optical fiber having a first end on the solid crystal side, a second end, a first lens provided facing the second end of the first optical fiber, and a first converging lens An acoustooptic device capable of transmitting a photon when no radio wave is applied and changing a traveling direction of the photon when a radio wave is applied, and the acoustooptic device provided near the acoustooptic device, and transmitting the acoustooptic device. A second lens capable of converging photons and an optical resonator mode that reflects the photon converged by the second lens and resonates with the transition energy of the physical system between the first reflecting mirror and the first lens. Second anti-cavity that can form an optical resonator Quantum information, comprising: a mirror; a third lens that converges the photon whose traveling direction is changed by an acousto-optic element; and a photodetector that detects the photon converged by the third lens. A processing device is provided.
[0024]
The photons converged by the lens may be a single photon or a photon beam of a set of photons.
[0025]
According to the first to sixth aspects of the present invention, an optical resonator using an optical fiber having a long resonator lifetime and a small resonator volume (mode volume) is used. And, when coupling between qubits in the resonator mode is required, such as 2-qubit operation, the qubit is coupled with the resonator mode of the optical resonator and does not require coupling in the resonator mode. When reading qubits, an optical resonator such as a frequency domain quantum calculation is not switched by coupling to a propagation mode of an optical fiber as an optical waveguide having a photodetector on one end face instead of a resonator. It is possible to read out the result by using the light of the quantum calculation used with high efficiency.
[0026]
The physical system that bears the qubits related to the present invention includes atoms, ions, molecules, or an aggregate thereof dispersed in an amorphous state such as a solid crystal, glass, or a polymer plastic, or a substrate. The fine particles above can be used.
[0027]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments relating to a quantum information processing apparatus and a quantum information processing method of the present invention will be described below with reference to the drawings. In addition, the same code | symbol shall be attached | subjected to a common structure through embodiment and an Example, and the overlapping description is abbreviate | omitted. Each figure is a schematic diagram, and its shape, dimensions, ratio, and the like are different from those of an actual apparatus. However, these can be determined in consideration of the following description and known techniques.
[0028]
First, quantum information processing devices that use optical resonators, and in particular, introduce the interaction between qubits using the resonator mode of the optical resonator, and use the transition energy (frequency) specific to each qubit. A frequency domain quantum computer that performs individual operations of qubits will be described.
[0029]
  In the frequency domain quantum computer, a physical system (atom, ion, molecule, etc.) having three degenerated energy states is used as a qubit. The three states are in ascending order of energy.| A _± >,| B _± >,｜ e _± >Then,| A _± >,| B _± >Uses a level with a long relaxation time,| A _± >−｜ e _± >while,| B _± >−｜ e _± >Inter-transitions that allow light are used. When the physical system is not subject to gate operation, the information of 1 qubit is | 0> ≡ at the lowest level.| A ₊ >, | 1> ≡| A ₋ >Is held like. In general, a qubit is a quantum mechanical superposition of two states, | 0> and | 1>.
  α | 0> + β | 1> (α and β are complex numbers) (1)
It has become.
[0030]
  These physical systems are in optical resonators, one of their allowed transitions, for example| B _± >−｜ e _± >The transition between is resonating with a common resonator mode.
[0031]
  Quantum state manipulation of one qubit, called one qubit gate, that is, manipulation of the values of α and β in equation (1)| A _± >It can be performed using resonance Raman transition in the state of
[0032]
The control NOT gate, which is one of the conditional gates between two qubits, called a two qubit gate, does not change the state of the second qubit if the first qubit is in the state | 0> If the first qubit is | 1>, the second qubit is a quantum gate that changes from | 0> to | 1> or from | 1> to | 0>. To execute this between the kth and lth qubits:
[0033]
  First,| A _± > _k When| A _± > _l Qubits held in| 0> _k =| B ₋ > _k ,｜ 1> _k =| A ₋ > _k ,| 0> _l =| B ₋ > _l ,｜ 1> _l =| B ₊ > _l Move to. Here, the subscripts attached to the symbols representing the respective states indicate that they relate to the kth and lth qubits. To do so, apply a magnetic field,h ・ ν _{a, ± , i} ,h ・ ν _{b, ± , i} Had energy (level energy)| A _± > _i When| B _± > _i , And induce an energy shift according to the magnetic quantum number,h ( ν _{a, ± , i} ± △ ν _a ),h ( ν _{b, ± , i} ± △ ν _b )And Here, h is a Planck constant. In this state, the frequency difference isν _{b, ± , k} −ν _{a, ± , k} -△ ν _b -△ ν _a ,ν _{b, ± , l} −ν _{a, ± , l} - △ ν _b -△ ν _a ,ν _{b, ± , l} ―Ν _{a, ± , l} + △ ν _b + △ ν _a By irradiating three sets of laser pulses at an appropriate timing,| 0> _k =| B ₋ > _k ,｜ 1> _k =| A ₋ > _k ,| 0> _l =| B ₋ > _l ,｜ 1> _l =| B ₊ > _l The state can be changed as follows.
[0034]
  Next, the qubit of the kth physical system is transferred to the lth physical system.| A _± > _l −｜ e _± > _l Irradiate the first laser pulse that resonates with the transition and overlap with it in time| A _± > _k −｜ e _± > _k By irradiating the second laser pulse that resonates with the transition, quantum information can be transferred between the k-th and l-th atoms by a technique called adiabatic passage. In this method, the physical system changes while maintaining the eigenstate consisting of the lower two levels, the state changes without being excited by the uppermost level, and the quantum information moves. Therefore, even though light that resonates with the transition to the top state is used, the transition to that state does not occur, and the quantum information is destroyed by a random process of spontaneous emission from the top state. Can be prevented. The adiabatic passage method of changing the lower level superposition state from time to time while maintaining the eigen state can be used even in the case of a one-qubit gate.
[0035]
As described above, as a result of the adiabatic passage between the kth and lth physical systems, the two qubits (quantum information) represented by the kth and lth physical systems are l It is represented only by the second physical system.
[0036]
  In the final stage of the control NOT gate,| A ₋ > _l When| A ₊ > _l The| A _± > _l −｜ e _± > _l Swap with a Raman transition with two lasers that resonate with the transition. This replacement｜ 1> _k | 0> _l When｜ 1> _k ｜ 1> _l Therefore, a conditional gate operation is executed here. After that, one of the qubits (quantum information) is returned to the kth physical system again by the adiabatic passage, and in each of the kth and lth physical systems| A _± > _k When| A _± > _l Stored in
[0037]
It is known that an arbitrary quantum operation can be performed by a combination of such a control NOT gate and one qubit gate.
[0038]
The frequency domain quantum computer repeats the above gate operation with a laser while applying an external field to perform a desired quantum operation.
[0039]
  And when reading the calculation result,| A _± >Ie| A ₊ >When| A ₋ >The qubits stored in| A ₋ >,| B ₋ >To the physical system that holds each qubit.| A _± >-| E _± >Irradiate a laser that resonates with the transition. If a photon is emitted from the i-th physical system, the physical system is| A ₋ > _i It can be seen that the qubit is | 0>, and if no photons are emitted, the physical system is| B ₋ >It can be seen that the state, that is, the qubit is | 1>.
[0040]
  By the way, the emitted photons｜ e _± >From| B _± >And is generated in the optical resonator as photons in the optical resonator mode. Although this photon must be detected, a quantum computer that introduces an interaction between qubits by a resonator mode requires a resonator having a long resonator lifetime. For this reason, photons existing in the resonator mode hardly come out of the resonator. Therefore,| A _± >−｜ e _± >After irradiating a laser that resonates with the transition, a large uncertainty occurs at the time when photons can be detected. Moreover, while staying in the resonator for a long time, photons leak out of the resonator due to imperfections in the resonator. The cause is scattering due to slight unevenness on the reflector surface, scattering due to the substance inside the resonator including the physical system used as a qubit, and leakage due to the fact that the resonator is not a space completely covered by the reflector. Due to various factors such as (diffraction), the direction in which photons emerge from the optical resonator cannot be predicted.
Due to the uncertainty of the photon-detectable time and the uncertainty of the direction in which the photons can be detected, it is necessary to wait for a long time to detect photons while keeping the detector highly sensitive. It is necessary to prepare a detector so that photons coming out in any direction can be captured. It is very difficult to increase the ratio of the detection signal to noise, and it is extremely difficult to detect generated photons with high efficiency. It becomes difficult.
[0041]
  A method of shifting each quantum state energy by applying an external field such as a magnetic field, an electric field, or a pressure is also conceivable so that photon emission to a common resonator mode used for qubit coupling does not occur. For example, qubits| A ₊ >,| A ₋ >Applying a magnetic field while maintaining| A ₊ >,| A ₋ >Split the energy of the state of| A ₊ >The photons emitted by irradiating a laser that resonates with a transition between || e> are observed, or the photons whose photon energy is changed are simply observed by applying a magnetic field last in the reading process.
[0042]
However, even in that case, if the resonator is completely close, there is a possibility that the resonator mode exists because photons are generated, the lifetime in the resonator may be long, and even if the resonator is incomplete Even if the generated photons quickly go out of the resonator, the direction cannot be determined, and it is still difficult to detect the generated photons with high efficiency.
[0043]
Therefore, in one embodiment of the present invention, an optical resonator using an optical fiber having a long resonator lifetime and a small resonator volume, which is suitable for a quantum computer that couples qubits in the resonator mode of the optical resonator, For quantum operations that require a resonator mode, the qubit is coupled to a common resonator mode, and when reading results that do not require the resonator mode, an optical fiber that connects to the photodetector instead of the resonator mode. Is switched so as to be coupled with the propagation mode of, so that detection of generated photons with high efficiency becomes possible. Moreover, this switching is performed between the optical fiber connected to the excitation light source, the optical fiber part of two resonators having such a structure is coupled, or the position of the resonator is small and the position control between the reflecting mirrors is easy. It is possible to further improve the ability of the quantum computer by changing the resonator mode by utilizing the above.
[0044]
Specific examples thereof will be described below through examples.
Example 1
FIG. 1 is a schematic side view illustrating a quantum information processing apparatus according to Embodiment 1 of the present invention.
[0045]
First, 0.05at.% Pr of 5mm x 5mm x 2mm³⁺Plate-like Y with ions dispersed₂SiO_FiveCrystal 1 (Mother Y³⁺0.05% of ions are Pr³⁺A material in which a dielectric multilayer film 3 having a reflectivity of 99.99% or more at 606 nm was prepared on one side of (substituted by ions) was prepared. An aluminum layer 5 is deposited on the surface of the crystal with dielectric multilayer film, and the surface on which the aluminum layer 5 of the multilayer crystal is further deposited is electrostatically applied to one surface of a glass substrate 7 of 5 mm × 5 mm × 5 mm. Glued.
[0046]
Then Y₂SiO_FiveCrystal 1 was polished to a thickness of 100 nm, and a thin film ion-dispersed crystal having a high reflectance mirror on the back surface was produced on glass substrate 7. Y of this glass substrate 7₂SiO_FiveThe surface opposite to the surface to which the crystal 1 was bonded was attached to the Invar casing 9.
[0047]
Further, both end faces of a single mode optical fiber 11 having a core diameter of 5 μm and a length of 1 mm were polished, and a dielectric multilayer film 13 having a reflectivity at 606 nm of 99.99% or more was produced on one end face. In addition, a photon detector 17 (Geiger mode avalanche photodiode cooled to liquid nitrogen temperature) is connected to one side of a multi-mode fiber 15 having a core diameter of 50 μm, and the other end surface is polished to obtain two optical fibers. The polished openings were bundled so that they were aligned, and attached to the optical fiber holder 19 connected to the piezo element attached to the Invar casing. The distance between the centers of the two fiber openings was 100 μm.
[0048]
Also, the opening surface of the two optical fibers is Y₂SiO_FiveY at a position about 10 nm away from the surface of the crystal₂SiO_FiveA piezo element 21 was installed so that it could move parallel to the crystal surface. As the piezo element 21, an element capable of taking a moving distance of 100 μm or more was used. Y₂SiO_FiveY so that a magnetic field can be applied to the crystal.₂SiO_FiveA coil 23 was provided in the vicinity of the crystal. In the drawings, the relative sizes of the respective parts are appropriately changed for easy illustration.
[0049]
As shown in the block diagram of FIG. 2, the light source unit detects light from the ring dye laser 27 excited by the argon ion laser 25 and detects the deviation from the resonance frequency of the reference optical resonator to obtain the laser frequency (wavelength). 16502.3cm narrowed to a frequency width of 5kHz using a frequency narrowing system that applies feedback^-1A light 31 (about 606 nm) was prepared. The light is further divided into two beams, each of which is passed through an acoustooptic device 33 for frequency modulation, and the frequency can be finely adjusted.³⁺Ionic^ThreeH_Four(1)-¹D₂(1) Adjust the laser resonating between transitions with a frequency accuracy within 5kHz.₂SiO_FiveThe crystal 1 can be irradiated. here^ThreeH_Four(1),¹D₂(1) in (1) indicates that each quantum state is one of the split states (Stark levels).
[0050]
  Y prepared as above₂Sio₅The system containing the crystal is placed in the cryostat together with the Invar casing 9, cooled to 3.8K, and the Pr³⁺Quantum states of ions³H₄(1) was used as a qubit.³H₄In the description of the frequency domain quantum computer, (1) is one of the three splits due to the nuclear spin state, for example, the nuclear spin ± 5/2 state.| A _± >Is equivalent to¹D₂(1) is｜ e _± >It corresponds to.
[0051]
This Y₂SiO_FiveA portion of the crystal 1 facing the opening of the optical fiber having the dielectric multilayer film 13 on the end face is irradiated with light from the light source unit shown in FIG. 2 while adjusting the frequency, and ions that are not used in the quantum operation are involved in the quantum operation. Pre-processing by an optical pump was performed so that a quantum state other than the quantum state was obtained, and then quantum computation was performed while appropriately adjusting the irradiation light frequency and the applied magnetic field. At this time, as shown in the schematic partial cross-sectional view of FIG. 3, an optical resonator having a small resonator volume and a long resonator lifetime is connected via a core 37 of the single-mode optical fiber 11 for optical resonators to the Y resonator.₂SiO_FiveThe dielectric multilayer film 3 provided on the back surface of the crystal 1 and the dielectric multilayer film 13 provided on the end face of the optical fiber 11 were used. And Pr of the area | region 35 facing the opening part of the optical fiber 11 with the dielectric material multilayer film 13 is shown.³⁺Among the ions, ions coupled by the resonator mode were used as qubits.
[0052]
After completing a series of quantum operations in the resonator, the piezo element 21 opens the openings of the optical fibers 11 and 15 to Y₂SiO_FiveThe region 35 where ions distributed as qubits are moved parallel to the surface of the crystal 1 over 50 μs so that it now faces the opening of the multimode fiber 15 connected to the photon detector 17. .
[0053]
  Next, Pr used as a qubit from the light source while appropriately adjusting the irradiation light frequency and applied magnetic field³⁺Y for ion₂Sio₅Irradiate light on the surface of crystal 1 from an oblique direction,| A ₊ >When| A ₋ >The qubits stored in| A ₋ >,| B ₋ >Moved to. Next, as shown in the schematic partial sectional view of FIG.| A _± >−｜ e _± >Laser 41 that resonates with the transition₂Sio₅When the surface of crystal 1 is irradiated from an oblique direction, ions are| A ₋ >The photon 43 generated in this state can be detected with high efficiency by the photon detector 17 connected to the multimode fiber 15, and therefore the calculation result can be read with high accuracy.
[0054]
(Example 2)
Next, a quantum information processing apparatus according to Embodiment 2 of the present invention will be described with reference to a schematic side view of FIG.
[0055]
First, the third single-mode optical fiber 45 whose end face is polished so as to align the opening face is added to the bundle of the optical fiber 11 for the optical resonator and the optical fiber 15 for reading in the first embodiment, and the end face opposite to the opening face. In addition, the light from the light source unit 47 can be incident. The light source unit 47 is the same as that described in the first embodiment with reference to FIG.
[0056]
At the time of reading in the first embodiment, the light from the light source unit 47 is incident on the third optical fiber, and resonates with the | a ±> − | e ±> transition in order for each ion used as a qubit. The optical fiber 15 connected to the photon detector is moved so that the opening of the optical fiber 15 faces the ions used as qubits, and if there is an emitted photon, it is read out. The calculation result was read by repeating the operation. The light from the light source unit 47 is Y except when reading.₂SiO_FiveThe crystal 1 can also be irradiated directly.
[0057]
As a result, the ions irradiated with light can be narrowed as compared with the case of irradiating the excitation light obliquely with respect to the surface of the thin film crystal through free space as in Example 1, and as a qubit Among the unused ions, ions that could not be transferred to a state where they did not interact with irradiation light in the pretreatment were excited, and reading errors due to emission of photons could be reduced.
[0058]
(Example 3)
Example 3 according to the present invention will be described with reference to the schematic side view of FIG.
[0059]
First, Y with the dielectric multilayer film of Example 1₂SiO_FiveA case in which a second piezoelectric element with an optical fiber holder was attached to a housing 9 provided with the crystal 1 and the piezoelectric element 21 was prepared.
[0060]
That is, as shown in FIG. 6, the dielectric multilayer film 13 is removed from the end face of the optical fiber 11 for an optical resonator used in Example 1 with the dielectric multilayer film 13 and the removed end face is polished, and this end face is polished. And the second readout multimode optical fiber 48 were combined, and the openings of both were aligned and installed in the second optical fiber holder. And the piezoelectric element which has the structure equivalent to the piezoelectric element 21 demonstrated in Example 1 and drives a 2nd optical fiber holder was installed.
[0061]
Furthermore, the light from the light source unit in Example 1 faces both openings of the optical fiber 11 for two optical resonators.₂SiO_FiveThe ions in the crystal 1 can be irradiated.
[0062]
As a result, Y₂SiO_FiveIt has become possible to execute a series of quantum operations using qubits in the two groups, each of which has a group of ions in two different locations in the crystal 1 as a qubit group. In other words, if there are two locations within reach of the optical fiber 11 used as an optical resonator, the ions in the thin film crystals at the two locations can be in a quantum mechanical entangled state, and in one quantum calculation It became possible to use.
[0063]
Example 4
Next, a fourth embodiment related to the present invention will be described with reference to a schematic side view of FIG.
[0064]
In Example 4, the opening of the optical fiber is set to Y₂SiO_FiveIn addition to moving in the direction along the surface of the crystal 1 (y direction in FIG. 7), Y₂SiO_FiveIt was replaced with an optical fiber driving unit 49 in which a piezo element capable of changing the distance from the crystal 1 (the x direction in FIG. 7) was also assembled.
[0065]
As a result, the common resonator mode that couples the qubits in the quantum operation can be changed, and when the common resonator mode is fixed, it does not resonate with the resonator mode, Ions that could not be used as qubits can now be used as qubits.
[0066]
(Example 5)
8 and 9 are diagrams for explaining the quantum information processing apparatus according to the fifth embodiment. FIG. 8 is a schematic side view of the apparatus. In Example 1, the drive unit by the piezo element was replaced with a part of an optical fiber holder having no drive function, and a single optical fiber was used instead of a bundle of optical fibers, and a dielectric multilayer film of the optical fiber for the resonator was attached. The dielectric multilayer film was removed from the end face, and an antireflection film was produced on the polished end face.
[0067]
In addition, an Invar substrate 51 on which a micro optical system is arranged is connected to this end face, and a photon detector 17 is connected to the Invar substrate 51 via a readout optical fiber 15.
[0068]
FIG. 9 is an enlarged schematic view showing the inside of the Invar substrate 51. A dotted line in FIG. 9 indicates an optical path. The Invar substrate 51 has the following optical system on its surface. This optical system has a first small converging lens 53 that converges light emitted from the optical fiber 11, and light loss at 606 nm that deflects light converged by the lens 53 when a radio wave is applied. A microacoustic optical element 55, a second microlens 57 that converts light emitted without being deflected from the acoustooptic element 55 into parallel light, and a reflectance at 606 nm that reflects the parallel light is 99.99% or more. And an optical system including a third minute lens 61 for converging light emitted after being deflected.
[0069]
Further, the readout optical fiber 15 for allowing the light converged by the third lens to enter was connected to the Invar substrate 51, and the other end face thereof was connected to the photon detector 17 as shown in FIG.
[0070]
With such a configuration, the operation was performed in the same manner as in Example 1 except for the result reading, and a radio wave was applied to the microacoustic optical element 55 when the result was read. As a result, if it is not read, Y₂SiO_FiveAn optical resonator is constituted by the dielectric multilayer film 3 on the back surface of the crystal 1 and a minute dielectric multilayer film mirror 59 on the Invar substrate 51, so that quantum operation can be performed, and the generated photon is a photon detector during reading. The results were read efficiently.
[0071]
In this embodiment, in order to reduce the mode volume of the optical resonator as much as possible, a micro acousto-optic effect element is used as an element for deflecting light, not an electro-optic effect element or a normal size acoustic effect element. Yes.
[0072]
(Example 6)
Pr in Example 1³⁺Y with dispersed ions₂SiO_FiveInstead of single crystal 1, Pr³⁺The same apparatus as in Example 1 was assembled and the same operation was performed using glass in which ions were dispersed at a concentration of 100 times. As a result, Pr in the frequency space³⁺The range in which ions are distributed is wide, and it is possible to distinguish more qubits in a frequency space with a laser with a wider frequency width, and quantum operations with more qubits are possible. The calculation result could be read efficiently as in the first embodiment.
[0073]
As mentioned above, although embodiment of this invention was described, this invention is not restricted to these, In the category of the summary of the invention as described in a claim, it can change variously.
[0074]
【The invention's effect】
As described above, according to the present invention, photon detection, that is, reading of a result can be performed with high efficiency. In addition, the quantum information processing ability can be improved.
[Brief description of the drawings]
FIG. 1 is a schematic side view for explaining a quantum information processing apparatus and a processing method according to Embodiment 1 of the present invention.
FIG. 2 is a block diagram schematically showing a light source unit in Embodiment 1 of the present invention.
3 is a cross-sectional view schematically showing a relationship between a position of an optical fiber opening of the quantum information processing method and quantum information processing apparatus according to Embodiment 1 of the present invention and a region where ions used as qubits are distributed. FIG.
4 schematically shows the relationship between the position of the optical fiber opening of the quantum information processing method and quantum information processing apparatus according to Embodiment 1 of the present invention and the region where ions used as qubits are distributed in the case of calculation result readout. FIG. FIG.
FIG. 5 is a schematic side view for explaining a quantum information processing apparatus and processing method according to Embodiment 2 of the present invention.
FIG. 6 is a schematic side view for explaining a quantum information processing apparatus and a processing method according to Embodiment 3 of the present invention.
FIG. 7 is a schematic side view for explaining a quantum information processing apparatus and a processing method according to Embodiment 4 of the present invention.
FIG. 8 is a schematic side view for explaining a quantum information processing apparatus and a processing method according to Embodiment 5 of the present invention.
FIG. 9 is an enlarged schematic view of an Invar substrate surface in the quantum information processing apparatus and processing method according to the fifth embodiment.
[Explanation of symbols]
1 ... Y₂SiO_Fivecrystal
3. Dielectric multilayer film
5 ... Aluminum layer
7 ... Glass substrate
9 ... Invar casing
11 ... Single mode optical fiber
13 ... Dielectric multilayer film
15 ... Multimode optical fiber for reading
17 ... Photon detector
19 ... Optical fiber holder
21 ... Piezo element
23 ... Coil
25 ... Argon ion laser
27. Ring dye laser
29 ... Frequency narrowing system
31 ... 16502.3cm^-1Laser
33 ... Acousto-optic device
35: Region where ions used as qubits are distributed
37, 39 ... Optical fiber core
41... | A ±> − | e ±> laser resonant with transition
43 ... Photons generated during reading
45 ... Third single mode optical fiber
47 ... Light source
48 ... second readout multimode optical fiber
49: Optical fiber drive unit
51 ... Invar substrate
53 ... 1st lens
55. Acousto-optic element
57 ... second lens
59 ... Dielectric multilayer mirror
61 ... Third lens

Claims (10)

A physical system containing atoms, ions or molecules dispersed in a solid material is positioned between a first reflecting mirror and a first end of a first optical fiber, and the first reflecting mirror and the first optical fiber Forming an optical resonator in which one of the resonator modes resonates with the transition energy of the physical system between the second reflecting mirror located at the second end of
Irradiating the physical system with light from outside the optical resonator to manipulate the quantum state of the physical system;
After finishing the operation step, the first end of the second optical fiber is changed to the first end of the first optical fiber, and the second optical system is placed at a position where the physical system is sandwiched between the first optical reflector and the second optical fiber. Moving the first end of the optical fiber;
After the moving step, the physical system is irradiated with light, photons emitted from the physical system are taken into the second optical fiber from the first end of the second optical fiber, and the second optical fiber is taken into the second optical fiber. Detecting with a combined photodetector;
A quantum information processing method comprising: determining a quantum state of the physical system based on the presence or absence of the photon detected in the detection step. A step of holding the first end of the third optical fiber at a position sandwiching the physical system with the first reflecting mirror, and the third end from the second end of the third optical fiber after the holding step. The quantum information processing method according to claim 1, further comprising: irradiating the physical system with light through the first end of the optical fiber and the third optical fiber. The quantum information processing method according to claim 1, further comprising a step of changing a resonator length of the optical resonator by changing a distance between the physical system and the first end of the first optical fiber. . A first physical system comprising atoms, ions or molecules dispersed in a solid material, located between the first reflector and the first end of the first optical fiber, and atoms dispersed in the solid material; A second physical system containing ions or molecules is positioned between the second reflecting mirror and the second end of the first optical fiber, and between the first reflecting mirror and the second reflecting mirror. Forming an optical resonator in which one of the resonator modes resonates with the transition energy of the first and second physical systems;
Manipulating the quantum state by irradiating the first or second physical system with light from outside the optical resonator;
After the operation step is finished, the first end of the second optical fiber is changed to the first end or the second end of the first optical fiber, and the first end of the second optical fiber is changed to the first or second end. A step of moving the first or second physical system between the reflecting mirror and
After the moving step, the first or second physical system facing the first end of the second optical fiber is irradiated with light, and photons emitted from the physical system are emitted from the second optical fiber. Taking into the second optical fiber from one end and detecting with a photodetector coupled to the second optical fiber;
And a step of determining a quantum state of the first or second physical system based on the presence or absence of the photon detected in the detection step. A physical system containing atoms, ions, or molecules dispersed in a solid material is positioned between the first reflecting mirror and the first end of the first optical fiber, and the first optical fiber is connected via an acoustooptic device. Light in which one of the resonator modes resonates with the transition energy of the physical system between the first reflecting mirror and the second reflecting mirror using the second reflecting mirror facing the second end. Forming a resonator; and
In a state where no radio wave is applied to the acoustooptic device, a step of irradiating the physical system with light from outside the optical resonator to manipulate the quantum state of the physical system;
Irradiating the physical system with light to emit photons from the physical system, and deflecting the traveling direction of the emitted photons by the acoustooptic device to which radio waves are applied;
And a step of detecting the presence or absence of the photons deflected by the deflection step. A plate-like or thin-film solid substance containing a physical system containing atoms, ions, or molecules, and having a first reflecting mirror formed on one side;
A first optical fiber comprising a first end on the solid material side and a second end;
An optical resonator provided at the second end of the first optical fiber and having an optical resonator mode that resonates with transition energy of the physical system is formed between the first optical fiber and the first reflecting mirror via the first optical fiber. A possible second reflector,
A second optical fiber comprising a first end on the solid material side and a second end connected to a photodetector;
Light irradiation means capable of irradiating light from the outside of the optical resonator and manipulating the quantum state of the physical system;
A measuring means capable of emitting light from the physical system by irradiating light to the physical system having a changed quantum state;
The first surface of the first optical fiber and the first end of the second optical fiber are opposed to the surface of the solid material opposite to the surface on which the first reflecting mirror is provided, and the opposite surface A support that can be moved in parallel with
During the operation of the light irradiating means, the supporting body is held at the first position so that the first end of the first optical fiber sandwiches the physical system with the first reflecting mirror, and the measuring means During the operation, the support is held in the second position so that the first end of the second optical fiber sandwiches the physical system with the first reflecting mirror, and the support is held in the first position. A quantum information processing apparatus comprising: a support moving unit that can be moved between the first and second positions. A third optical fiber having a first end and a second end on the solid material side, and a light source connected to a second end of the third optical fiber,
The support has a first end of the first optical fiber, a first end of the second optical fiber, and a first end of the third optical fiber provided with the first reflecting mirror of the solid material. And can be moved in parallel with the opposite surface,
The support moving unit is configured to irradiate the physical system with light from the light source via the third optical fiber, and the first end of the third optical fiber is between the first reflecting mirror and the first reflecting mirror. The quantum information processing apparatus according to claim 6, wherein the support can be positioned so as to sandwich a physical system. The quantum information processing method according to claim 6, wherein the support moving unit is capable of changing a distance between the physical system and the first end of the first optical fiber via the support. . A first solid material containing a first physical system containing atoms, ions, or molecules and having a first reflecting mirror formed on one side, and a second solid containing atoms, ions, or molecules. A plate-like or thin-film-like second solid substance containing a physical system inside and having a second reflecting mirror formed on one side;
A first end on the first physical system side and a second end on the second physical system side, the first and second reflectors between the first and second reflectors A first optical fiber capable of forming an optical resonator having an optical resonator mode that resonates with transition energy of a physical system;
A second optical fiber comprising a first end on the first solid material side and a second end connected to a first photodetector;
A third optical fiber comprising a first end on the second solid material side and a second end connected to a second photodetector;
A light irradiating means capable of operating the quantum state of the first or second physical system by irradiating light from outside the optical resonator;
A measurement means capable of irradiating the first or second physical system having a changed quantum state with light and emitting photons from the first or second physical system irradiated with the light;
A first set of the first end of the first optical fiber and the first end of the second optical fiber is placed on a surface opposite to the surface on which the first reflecting mirror of the first solid material is provided. The second set of the second end of the first optical fiber and the first end of the third optical fiber can be moved in parallel with the opposite surface. A support that can be moved parallel to the surface opposite to the surface of the second solid substance, opposite to the surface opposite to the surface on which the second reflecting mirror of the solid material is provided;
During the operation of the light irradiation means, the first end of the first optical fiber is sandwiched between the first physical system and the first end of the first optical fiber, and the second end of the first optical fiber is The support is held at the first position so that the second physical system is sandwiched between the second reflecting mirror and the first end of the second optical fiber is moved when the measuring means is operated. The first physical system is sandwiched between the first reflecting mirror or the second physical system is sandwiched between the first end of the third optical fiber and the second reflecting mirror. A quantum information processing apparatus, further comprising: a support moving unit that holds the support in a second position and moves the support between the first and second positions. A plate-like or thin-film solid substance containing a physical system containing atoms, ions, or molecules, and having a first reflecting mirror formed on one side;
A first optical fiber comprising a first end on the solid material side and a second end;
A first lens provided facing the second end of the first optical fiber;
An acoustooptic device that is provided in the vicinity of the first lens and is capable of transmitting photons when no radio wave is applied and changing the traveling direction of the photons when a radio wave is applied;
A second lens provided in the vicinity of the acoustooptic element and capable of converging the photons transmitted through the acoustooptic element;
A second reflection capable of forming an optical resonator having an optical resonator mode that resonates with the transition energy of the physical system by reflecting photons converged by the second lens and resonating with the transition energy of the physical system. With a mirror,
A third lens for converging the photons whose traveling direction has been changed by the acoustooptic device;
A quantum information processing apparatus comprising: a photodetector that detects the photons converged by the third lens.

Images