Quantum computer and quantum calculation method

Abstract

A quantum computer (100) comprises: an atomic ensemble (1) including a plurality of first atoms (11) and a plurality of second atoms (12) of different types; an optical tweezer array system (3) configured to generate an optical tweezer array for arranging atomic ensembles (11); a first probe light source (4) configured to emit first probe light for reading each of the plurality of first atoms (11) as a data qubit; and a second probe light source (5) configured to emit second probe light for reading each of the plurality of second atoms (12) as an auxiliary qubit. The auxiliary qubit is a nuclear spin qubit, an optical-transition qubit, or a fine-structure qubit.

Description

Quantum computers and quantum computing methods

[0001] This disclosure relates to quantum computers and quantum computing methods, and more specifically to neutral atom quantum computing-related technologies.

[0002] One promising technique for performing highly reliable computations in quantum computers, where qubit errors are inevitable, is quantum error correction (QEC). A suitable qubit array configuration for quantum error correction includes data qubits used for storing quantum information and auxiliary qubits for reading the quantum information stored in the data qubits.

[0003] In neutral atom (particularly neutrally cooled atom) quantum computers, spatial isolation and spectral isolation have been proposed and demonstrated as approaches for selectively reading either data qubits or auxiliary qubits. Spatial isolation is a method in which auxiliary qubits are spatially moved using dynamic optical tweezers to isolate them from data qubits, and then read out locally. Spectral isolation is a method in which data qubits are transitioned to a dark state (a state unaffected by probe light used to read out auxiliary qubits) by locally irradiating them with light. Both of these methods require localized light irradiation operations, which are technically difficult. Furthermore, spatial isolation incurs a significant time cost.

[0004] A third approach has been proposed for selectively reading either a data qubit or an auxiliary qubit, using two types of neutral atoms. Non-patent document 1 uses alkali atoms of different atomic species (specifically, 87-rubidium and 133-cesium atoms). Non-patent document 2 uses isotopes of the same atomic species of alkali atom (specifically, 87-rubidium and 85-rubidium atoms). Using two types of neutral atoms eliminates the need for localized light irradiation, thereby reducing technical difficulty and time costs.

[0005] K. Singh, CE Bradley, S. Anand, V. Ramesh, R. White, H. Bernien, Mid-circuit correction of correlated phase errors using an array of spectator qubits, Science 380, 1265-1269 (2023).Yong Zeng, Peng Xu, Xiaodong He, Yangyang Liu, Min Liu, Jin Wang, DJ Papoular, GV Shlyapnikov, Mingsheng Zhan, Entangling Two Individual Atoms of Different Isotopes via Rydberg Blockade, Physical Review Letters 119, 160502 (2017).

[0006] There is a demand for technologies that can adequately perform quantum error correction. One of the purposes of this disclosure is to provide a quantum computer and a quantum computing method that can adequately perform quantum error correction.

[0007] (1) A quantum computer according to a first aspect of the present disclosure includes a plurality of neutral atoms, including a plurality of first atoms and a plurality of second atoms of different kinds; an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of neutral atoms; a first probe light source configured to emit a first probe light for reading each of the plurality of first atoms as a data qubit; and a second probe light source configured to emit a second probe light for reading each of the plurality of second atoms as an auxiliary qubit. The auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

[0008] (2) A quantum computer according to a second aspect of the present disclosure includes a plurality of first atoms, a plurality of second atoms, an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of first atoms and the plurality of second atoms, a first probe light source configured to emit first probe light for reading each of the plurality of first atoms as a data qubit, and a second probe light source configured to emit second probe light for reading each of the plurality of second atoms as an auxiliary qubit. The plurality of first atoms and the plurality of second atoms are two types of atoms, which are different atomic species or different isotopes of each other, from among alkaline earth atoms and alkaline earth-like atoms.

[0009] (3) A quantum computing method according to a third aspect of the present disclosure includes the steps of preparing an atomic array of a plurality of neutral atoms, including a plurality of first atoms and a plurality of second atoms of different types, using an optical tweezers array; irradiating the atomic array with a first probe light to read each of the plurality of first atoms as a data qubit; and irradiating the atomic array with a second probe light to read each of the plurality of second atoms as an auxiliary qubit. The auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

[0010] In the configuration of (1) above, nuclear spin qubits, optical transition qubits, or microstructure qubits are used as auxiliary qubits. In the configuration of (2) above, alkaline earth atoms or alkaline earth-like atoms are used as auxiliary qubits. As will be described in detail later, nuclear spin qubits, optical transition qubits, and microstructure qubits, unlike the qubits used in Non-Patent Documents 1 and 2 (hyperfine structure qubits), can read out auxiliary qubits without causing atomic loss. Therefore, according to the configurations of (1) and (2) above, a quantum computer capable of appropriately performing quantum error correction can be provided. Furthermore, according to the method of (3) above, similar to the configuration of (1) above, auxiliary qubits can be read out without causing atomic loss, thus providing a quantum computing method capable of appropriately performing quantum error correction.

[0011] This disclosure provides a quantum computer and a quantum computing method capable of appropriately performing quantum error correction.

[0012] Figure 1 is a schematic diagram showing an example of the overall configuration of a quantum computer according to the embodiment of this disclosure. Figure 2 is a block diagram showing an example of the configuration of a controller. Figure 3 is a conceptual diagram showing an example of quantum error correction. Figure 4 is a diagram showing a qubit array in a comparative example. Figure 5 is a diagram for explaining a qubit in a comparative example. Figure 6 is a diagram showing a qubit array in this embodiment. Figure 7 is a diagram for explaining a qubit in this embodiment. Figure 8 is a diagram for explaining combinations of data qubits and auxiliary qubits when implemented with different atomic species. Figure 9 is a diagram for explaining combinations of data qubits and auxiliary qubits when implemented with different isotopes. Figure 10 is a flowchart showing an example of the processing procedure of the quantum computing method according to this embodiment. Figure 11 is a flowchart showing an example of the processing procedure for preparing a qubit array. Figure 12 is a time chart showing an example of optical operations in qubit array preparation. Figure 13 is an image of a captured atom ensemble. Figure 14 is a diagram for explaining photo-association by irradiation with photo-induced collision light. Figure 15 is a diagram showing an example of images of the qubit array before and after atomic rearrangement. Figure 16 shows an example of the coherence measurement results of a data qubit when an auxiliary qubit is read out. Figure 17 shows an example of the fidelity measurement results of an auxiliary qubit. Figure 18 shows an example of the verification results of single-atom bit generation using a heteronuclear photoassociation process.

[0013] <Explanation of Terms> In this disclosure and embodiments, “data qubit” means a qubit used to store data (quantum information). A data qubit may also be called an actual qubit.

[0014] In this disclosure and embodiments, "ancilla qubit" means a qubit used to read data stored in a data qubit. An auxiliary qubit may be used for error correction (quantum error correction) of the data qubit. An auxiliary qubit is also referred to in English as an auxiliary qubit or spectator qubit. An auxiliary qubit may also be called a measurement qubit.

[0015] In this disclosure and embodiments, “alkali atom” is a general term for atoms belonging to Group 1 of the periodic table (excluding hydrogen). Alkali atoms include lithium (Li), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), and francium (Fr).

[0016] In this disclosure and embodiments, “alkaline earth atoms” is a general term for atoms belonging to Group 2 of the periodic table. Alkaline earth atoms include beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), and radium (Ra).

[0017] In this disclosure and embodiments, "alkaline earth-like atom" refers to an atom that has two outermost electrons, similar to an alkaline earth atom. Alkaline earth-like atoms include ytterbium (Yb).

[0018] In this disclosure and embodiments, “different kinds” or “multiple kinds” of neutral atoms include, but are not limited to, two or more different atomic species, and also include two or more different isotopes of the same atomic species.

[0019] Embodiments of this disclosure will be described in detail below with reference to the drawings. In the drawings, the same or corresponding parts are denoted by the same reference numerals, and their descriptions will not be repeated. In the following description, the x and y directions represent the horizontal directions. The x and y directions are orthogonal to each other. The z direction represents the vertical direction. The direction of gravity is downward in the z direction. Upward in the z direction is abbreviated as "up," and downward in the z direction is abbreviated as "down."

[0020] [Embodiment] <System Configuration> Figure 1 is a schematic diagram showing an example of the overall configuration of a quantum computer according to the embodiment of this disclosure. The quantum computer 100 includes an atomic group 1 containing multiple types of neutral atoms, a vacuum device 2, an optical tweezers array system 3, a first probe light source 4, a second probe light source 5, an imaging system 6, and a controller 7.

[0021] Atomic group 1 includes a plurality of first atoms 11 (shown in black) and a plurality of second atoms 12 (shown in white). By arranging atomic group 1 in two dimensions, a qubit array (shown as "AR" in the figure) is generated. Each of the plurality of first atoms 11 functions as a data qubit. Each of the plurality of second atoms 12 functions as an auxiliary qubit. In this example, the first atoms 11 are 171 ytterbium ( １７１ Yb) is an atom, and the second atom 12 is 174 ytterbium ( １７４ It is a Yb atom.

[0022] However, the first atom 11 and the second atom 12 may be other isotopes of the ytterbium atom, or they may be alkaline earth atoms such as strontium or calcium atoms. The reasons for adopting alkaline earth atoms or alkaline earth-like atoms in this way will be explained in detail later.

[0023] The vacuum apparatus 2 is a high-vacuum optical chamber in which the atomic group 1 is housed. The vacuum apparatus 2 includes, for example, an atomic oven chamber for heating and sublimating solid neutral atoms, a Zeeman slowing pipe for performing Zeeman slowing on the atomic group 1 by the neutral atoms that have become gaseous, a pump chamber for creating a vacuum using a pump, and a scientific chamber in which a qubit array is arranged.

[0024] The optical tweezers array system 3 is configured to generate an optical tweezers array for arranging an atomic ensemble 1 in a two-dimensional manner within the scientific chamber of the vacuum apparatus 2. The optical tweezers array system 3 includes, for example, a Zeeman decelerating light source 31, a magneto-optical trap (MOT) device 32, an optical tweezers light source 33, a light-assisted collision (LAC) light source 34, a cooling light source 35, a first objective lens 36, a second objective lens 37, a spatial light modulator (SLM) 381, an acousto-optical deflector (AOD) 382, ​​and a plurality of optical components. The plurality of optical components include, for example, a lens 391, a dichroic mirror 392, a mirror 393, a dichroic mirror 394, a lens 395, a mirror 396, and a beam splitter 397.

[0025] The Zeeman deceleration light source 31 emits light for Zeeman deceleration (hereinafter referred to as "Zeeman deceleration light") in accordance with control commands from the controller 7. The Zeeman deceleration light source 31 decelerates the atomic group 1 emitted from the atomic oven chamber by irradiating it with Zeeman deceleration light from a direction opposite to it.

[0026] The magneto-optical trapping device 32 includes a coil for generating a magnetic field gradient and a light source for emitting light for magneto-optical trapping (hereinafter referred to as "MOT light"). The magneto-optical trapping device 32, in accordance with control commands from the controller 7, irradiates the atom group 1, which has been decelerated by Zeeman deceleration light, with MOT light from three mutually orthogonal directions and simultaneously applies a magnetic field gradient to trap the atom group 1. In this example, the first atom 11 ( １７１ MOT light for Yb atom and second atom 12 ( １７４ The MOT light for the Yb atom is tuned to propagate along the same path.

[0027] More specifically, the MOT light includes x-axis light, y-axis light, and z-axis light. The x-axis light (indicated as "MOTx") is irradiated onto the vacuum apparatus 2 from two opposing directions in the x-axis direction. The same applies to the y-axis light, which is not shown. The z-axis light (indicated as "MOTz") is focused by lens 391, reflected by dichroic mirror 392, and then reflected upward by mirror 393. This z-axis light is irradiated onto the vacuum apparatus 2 via the first objective lens 36. After passing through the vacuum apparatus 2, the z-axis light is reflected by dichroic mirror 394 and shaped into collimated light by lens 395. The collimated light is reflected by mirror 396 and further reflected by dichroic mirror 394 and directed downward. This z-axis light is irradiated onto the vacuum apparatus 2 via the second objective lens 37.

[0028] The optical tweezers light source 33 emits light for performing optical tweezers operations within the vacuum apparatus 21 according to control commands from the controller 7. In this example, an optical tweezers beam (indicated as "TW") for loading the atomic group 1 and generating a qubit array is generated using a spatial light modulator 381, and a dynamic optical tweezers beam (indicated as "mTW") for rearranging the qubit array to an arbitrary configuration is generated using an acousto-optic deflector 382. The optical tweezers beam passes through the beam splitter 397, through the dichroic mirror 392, is reflected by the mirror 393, and is focused at the focal plane of the first objective lens 36. The dynamic optical tweezers beam is reflected by the beam splitter 397, passes through the dichroic mirror 392, is reflected by the mirror 393, and is focused at the focal plane of the first objective lens 36.

[0029] The photo-induced collision light source 34 emits light (hereinafter referred to as "LAC light") that is adjusted to cause two-body loss due to photo-induced collisions at each site (lattice point) of the optical tweezers array, in accordance with control commands from the controller 7. As will be described in detail later, irradiation with LAC light reduces the number of atoms at each site to 0 or 1. In other words, a single-atom bit is generated.

[0030] The cooling light source 35 emits cooling light according to control commands from the controller 7. The cooling light is used to suppress heating caused by probe light (the first probe light or the second probe light described later) that occurs during imaging of the qubit array using probe light.

[0031] As in this example, multiple types of neutral atoms constitute atomic group 1. １７１ Yb atom and １７４ When Yb atoms are used, the wavelengths of light emitted from each light source can be set as follows. Light sources whose required optical frequencies are the same or close enough to be tuned by an acousto-optic element or electro-optic modulator may be shared. For example, the photo-induced collision light source 34 and the cooled light source 35 can be shared. • Zeeman deceleration light source: 399 nm • Magneto-optic trap device: 556 nm • Optical tweezers light source: 532 nm • Photo-induced collision light source: 556 nm • Cooled light source: 556 nm

[0032] Note that the optical system of the optical tweezers array system 3 shown in Figure 1 has been significantly simplified for the sake of space limitations. The optical tweezers array system 3 may include various optical components, optical modulators, etc., that are not shown.

[0033] The first probe light source 4 emits a first probe light (indicated as "P1") to read out each of the plurality of first atoms 11 as a data qubit, in accordance with a control command from the controller 7. The first probe light is irradiated onto the entire qubit array, for example, from a direction along the x-axis. The first probe light has a first wavelength. １７１ If it is a Yb atom, the first wavelength is 399 nm.

[0034] The second probe light source 5 emits a second probe light (indicated as "P2") to read out each of the multiple second atoms 12 as an auxiliary qubit, in accordance with a control command from the controller 7. The second probe light, like the first probe light, irradiates the entire qubit array from a direction along the x-axis. The second wavelength of the second probe light is 399 nm. However, since the first atom 11 and the second atom 12 are different isotopes, the first wavelength of the first probe light and the second wavelength of the second probe light differ due to the isotopic shift. Note that 556 nm can also be selected as the second wavelength. Even when the first and second wavelengths are selected as 556 nm, the first and second wavelengths will differ due to the isotopic shift.

[0035] When the first or second probe light is shone onto the entire qubit array, fluorescence (indicated as "FL") is generated from each qubit according to its state. The fluorescence is focused by the second objective lens 37, passes through the dichroic mirror 394, and is directed towards the imaging system 6 located above the optical tweezers array system 3.

[0036] The imaging system 6, in accordance with control commands from the controller 7, images the qubit array and outputs the captured image to the controller 7. The imaging system 6 includes, for example, a mirror 61, an imaging lens 62, and a camera 63. Fluorescence from the qubit array is reflected by the mirror 61 and then imaged onto the camera 63 by the imaging lens 62. Suitable cameras for the camera 63 include electron-multiplying charge-coupled devices (EMCCDs) and scientific CMOS (Complementary Metal Oxide Semiconductor) cameras.

[0037] Controller 7 is a conventional computer (classical computer). Controller 7 prepares the qubit array by controlling the components of the quantum computer 100 (optical tweezers array system 3, first probe light source 4, second probe light source 5, and imaging system 6). Controller 7 also executes a computation sequence based on the image captured by the imaging system 6.

[0038] Figure 2 is a block diagram showing an example of the configuration of the controller 7. The controller 7 includes a processor 71, a memory 72, an input device 73, an output device 74, and a communication interface 75.

[0039] The processor 71 includes arithmetic processing units such as a CPU (Central Processing Unit), an MPU (Micro Processing Unit), and a GPU (Graphic Processing Unit). The memory 72 includes volatile storage devices such as DRAM (Dynamic Random Access Memory) and SRAM (Static Random Access Memory), and non-volatile storage devices such as an HDD (Hard Disk Drive), an SSD (Solid State Drive), and flash memory.

[0040] Memory 72 stores a system program 721 including the OS (Operating System), a control program 722 for controlling the components of the quantum computer 100 (optical tweezers array system 3, first probe light source 4, second probe light source 5, and imaging system 6), and a calculation program 723 related to calculation sequences executed based on images captured by the imaging system 6. The processor 71 performs various processes by reading the system program 721, the control program 722, and / or the calculation program 723 and loading them into memory 72. The controller 7 may be configured by dividing it into two or more units for each function.

[0041] In this specification, the term "processor" is not limited to processors that execute processing using stored programs, but may also include hardwired circuits such as ASICs (Application Specific Integrated Circuits) and FPGAs (Field-Programmable Gate Arrays). Therefore, the term "processor" can also be interpreted as processing circuitry in which processing is predefined by computer-readable code and / or hardwired circuits.

[0042] The input device 73 is a keyboard, mouse, touch panel, operation buttons, etc., and is configured to accept operations from the user (measurer such as a researcher, developer, or student). The output device 74 is a monitor, printer, etc., and is configured to output the calculation results from the processor 71. The communication interface 75 is configured to send and receive various signals (control commands, images, data, etc.) with the components of the quantum computer 100.

[0043] <Quantum Bit Array> One of the main processes performed in the quantum computer 100 according to this embodiment is quantum error correction.

[0044] Figure 3 is a conceptual diagram illustrating an example of quantum error correction. For simplicity, Figure 3 shows a quantum circuit of a three-qubit repeating code. Controller 7 is configured to perform quantum error correction by mid-circuit correction of the qubit array. In other words, controller 7 detects and corrects errors in the data qubits based on feedback of measurement results of auxiliary qubits that are entangled with the data qubits, not only at the end of the computation sequence but at various points in time. To realize such mid-circuit correction, the qubit array must be configured so that auxiliary qubits can be read out without affecting the data qubits.

[0045] In order to facilitate understanding of the qubit array according to the present embodiment, the qubit array according to a comparative example will be first described.

[0046] <<Comparative Example>> FIG. 4 is a diagram showing a qubit array according to the comparative example. Both a first atom 91 and a second atom 92 in the comparative example are alkali atoms. In this case, both a data qubit and an auxiliary qubit are hyperfine structure qubits.

[0047] FIG. 5 is a diagram for explaining a qubit (hyperfine structure qubit) according to the comparative example. FIG. 5 shows 85-rubidium ( ８５ Rb) atom, 87-rubidium ( ８７ Rb) atom and 133-cesium ( １３３ Cs) atom, which are typical alkali atoms employed in neutral atom quantum computers, along with energy level diagrams thereof.

[0048] Since all alkali atoms have a nuclear spin, hyperfine structures resulting from the interaction between nuclear spin and electron spin exist in alkali atoms, in addition to fine structures resulting from the interaction between electron orbital angular momentum and electron spin. Specifically, ８５ the ground state of an Rb atom (nuclear spin I=5 / 2) ２ S １／２ has hyperfine structures with total angular momentum F=2 and F=3. ８７ the ground state of an Rb atom (nuclear spin I=3 / 2) ２ S １／２ has hyperfine structures with total angular momentum F=1 and F=2. １３３ the ground state of a Cs atom (nuclear spin I=7 / 2) ２ S １／２ has hyperfine structures with total angular momentum F=3 and F=4. A plurality of magnetic quantum numbers m Ｆ exists for each hyperfine level.

[0049] In the hyperfine structure qubit of the comparative example, a state |0> and a state |1> are described using a transition between two hyperfine levels in the ground state of an alkali atom (hereinafter referred to as "hyperfine transition").

[0050] For example, Non-Patent Document 1 describes two types of alkali atoms. ８７ Rb atom and １３３ The hyperfine structure transitions of each ground state of the Cs atom are used. In the data qubit of Non-Patent Literature 1, ８７ Ground state of Rb atom ２ S １／２ Regarding the state | F = 1, m Ｆ State |0> is given by state |F=2,m Ｆ State |1> is when =0>. In the auxiliary qubit of Non-Patent Literature 1, １３３ Ground state of Cs atom ２ S １／２ Regarding the condition, F = 3, m Ｆ State |0> is state |F=4, m Ｆ State |1> is equal to state 0>.

[0051] Non-patent document 2 describes two isotopes of alkali atoms. ８７ Rb atom and ８５ The hyperfine structure transitions of each ground state of the Rb atom are used. The data qubit in Non-Patent Document 2 is the same as the data qubit in Non-Patent Document 1. In the auxiliary qubit of Non-Patent Document 2, ８５ Ground state of Rb atom ２ S １／２ Regarding the state, F = 2, m Ｆ State |0> is given by state |F=3,m Ｆ State |1> is equal to state 0>.

[0052] Furthermore, hyperfine structure qubits may also be called hyperfine structure clock transition bits. A clock transition refers to a transition with an extremely narrow resonance frequency bandwidth (usually around 10 mHz), and the hyperfine structure transitions used in hyperfine structure qubits satisfy this condition.

[0053] The present inventors focused on the fact that the methods described in Non-Patent Documents 1 and 2 have the following problems in principle. In alkali atom qubit arrays, for example, resonant light in state |1> is generally irradiated onto the entire qubit array to heat the auxiliary qubits in state |1>, thereby removing all auxiliary qubits in state |1>, and then the remaining auxiliary qubits in state |0> are read out. In other words, state-selective atomic loss occurs in each of the multiple auxiliary qubits, depending on the state of that auxiliary qubit. This can also be described as the readout of the auxiliary qubits being destructive.

[0054] In quantum error correction, auxiliary qubits are read out multiple times during the computation sequence. Therefore, to implement quantum error correction using an alkali atom qubit array, it is necessary to replenish the auxiliary qubits that are state-selectively removed by the readout with new alkali atoms each time an auxiliary qubit is read out. It is desirable to read out the auxiliary qubits non-destructively, without causing atomic loss. Therefore, in this embodiment, the following qubit array is employed.

[0055] ≪This Embodiment≫ Figure 6 shows a qubit array in this embodiment. In the example shown in Figure 6, the data qubit is a nuclear spin qubit, and the auxiliary qubit is an optical transition qubit. In other words, while two types of atomic species or isotopes are used in the comparative example, two types of qubits are used in this embodiment. These two types of qubits are implemented (realized) using alkaline earth atoms or alkaline earth-like atoms. In the example described in detail below, two isotopes of the Yb atom, which is an alkaline earth-like atom, are used.

[0056] Figure 7 is a diagram illustrating the qubit in this embodiment. Figure 7 shows the energy level diagram of a Yb atom.

[0057] There are seven stable isotopes of the Yb atom. Of these, five are ( １６８ Yb, １７０ Yb, １７２ Yb, １７４ Yb,１７６ Yb) is a boson isotope, and there are two types ( １７１ Yb, １７３ Yb is a fermionic isotope. The Yb atom in the fermionic isotope has nuclear spin I. １７１ The nuclear spin I of the Yb atom is 1 / 2. １７３ The nuclear spin I of the Yb atom is 5 / 2. Hyperfine fission of energy levels occurs only when the Yb atom is a fermionic isotope. In Figure 7, to avoid cluttering the paper, the ground state is shown. １ S ０ Only the ultrastructure is shown in the illustration.

[0058] The Zeeman deceleration explained in Figure 1 includes: １ S ０ - １ P １ A transition is used. This transition is an acceptable transition that satisfies the selection rules for electric dipole transitions. For magneto-optical traps (MOT), photo-induced collisions (LAC), and cooling, １ S ０ - ３ P １ A transition is used. This transition is a forbidden transition that does not satisfy the selection rules for electric dipole transitions, and is a completely closed cycle transition in which the electron falls to the ground state by spontaneous emission (in other words, a transition in which the atom does not transition to another state by allowed spontaneous emission). The total orbital angular momentum L of the electron system of a Yb atom is 1 ((6s6p)). 3 The P series includes, ３ P １ In addition to the condition ３ P ０ State and ３ P ２ A state exists. (6s6p) ３ P ０ State and ３ P ２ The state is a long-lived metastable state (metastable excited state).

[0059] The characteristics of each qubit used in this embodiment will be described below with reference to both Figure 6 and Figure 7.

[0060] ≪Nuclear Spin Qubits≫ In nuclear spin qubits, the state is described using the nuclear spin degrees of freedom of the ground state, and the nuclear spin carries the information. Nuclear spin qubits are implemented using fermion isotopes that have the nuclear spin of alkaline earth atoms or alkaline earth-like atoms.

[0061] In this example, １７１ A Yb atom (nuclear spin I = 1 / 2) is used as a nuclear spin qubit. Ground state １ S ０ The nuclear spin magnetic quantum number m Ｉ Regarding the status | m Ｉ = 1 / 2 > is state |0>, and state |m Ｉ State |1> is the state where -1 / 2 is the ground state. １ S ０ Metastable state ３ P ０ You may also use [this].

[0062] １７１ Fermion isotopes other than the Yb atom １７３ Yb atoms may also be used. Other neutral atoms besides ytterbium atoms include, for example, 87-strontium ( ８７ You may use Sr atoms, or 43 calcium ( ４３ Ca atoms may also be used.

[0063] In nuclear spin qubits, the polarization of the probe light is controlled under the application of a strong magnetic field, thereby controlling the state |m Ｉ = 1 / 2 > and state | m Ｉ It is possible to selectively emit light in one of the states || １ S ０ - ３ P １ It is preferable to use light with a wavelength of 556 nm, corresponding to the transition, as probe light.

[0064] ​Furthermore, nuclear spin is less susceptible to the influence of external magnetic fields. In addition, the shift of atomic energy levels (light shift) caused by trapping light (optical tweezer beam) is less dependent on nuclear spin. Therefore, long coherence times can be achieved with nuclear spin qubits. Specifically, while the coherence time of hyperfine structure qubits in alkali atoms is 1 to 10 milliseconds, the coherence time of nuclear spin qubits is on the order of seconds. In addition, nuclear spin qubits can be manipulated at high speed on the order of 100 nanoseconds to 1 microsecond via Raman transition through an excited state.

[0065] <<Optical Transition Qubit>> In an optical transition qubit, the state is described using the optical transition between a ground state and a metastable state, and the electron orbit carries information. For alkaline earth atoms or alkaline earth-like atoms, an optical transition qubit may be implemented using a boson isotope, or may be implemented using a fermion isotope.

[0066] In this example,[­ １７４ the ground state of a Yb atom １ S ０ and the metastable state ３ P ２ the optical transition between and is used. Specifically, the state | １ S ０ > is the state |0>, and the state | ３ P ２ > (magnetic sublevel m=0) is the state |1>. Alternatively, １７４ the ground state of a Yb atom １ S ０ and the metastable state ３ P ０ the optical transition between and can also be used. In that case, the state | １ S ０ > is the state |0>, and the state | ３ P ０ > is the state |1>.

[0067] As isotopes of Yb atoms,[­ １７４ In addition to Yb atoms, １６８ Yb atom, １７０ Yb atom, １７１ Yb atom, １７２ Yb atom, １７３ Yb atom or１７６ Yb atoms may also be used. As for strontium atoms, ８４ Sr atom, ８６ Sr atom, ８７ Sr atom or ８８ Sr atoms can be used. Calcium atoms can be used as follows: ４０ Ca atom, ４２ Ca atom, ４３ Ca atom, ４４ Ca atom, ４６ Ca atom or ４８ Ca atoms can be used.

[0068] In optical transition qubits, near-resonant light from the optical transition qubit is used as probe light to illuminate the entire qubit array, and readout is performed by detecting the fluorescence emitted from the optical transition qubit. Optical transition qubits in the ground state emit fluorescence when irradiated with probe light, while optical transition qubits in the metastable state do not emit fluorescence even when irradiated with probe light. Therefore, it is not necessary to remove qubits in state |1> when reading out qubits in state |0>. Thus, optical transition qubits can also be readout nondestructively. Furthermore, long coherence times can be achieved even with optical transition qubits.

[0069] In addition, generally, the resonance frequencies of transitions differ between isotopes (isotope shift), and in this example, two isotopes of the Yb atom are used as data qubits and auxiliary qubits. １７１ Yb atom and １７４ Yb atoms are used. Therefore, the first probe light used to read out the data qubit is non-resonant with respect to the auxiliary qubit. Conversely, the second probe light used to read out the auxiliary qubit is non-resonant with respect to the data qubit. In more detail, １７１ Yb atom and １７４ The isotopic shift between the Yb atom and the Yb atom is on the order of GHz. １ S ０ - １ P １ The natural width of the transition is 29 MHz and １ S ０ - ３ P １The transition frequency is significantly larger compared to the natural width of 182 kHz. Therefore, neither the first probe light nor the second probe light causes atomic loss in the data qubit. Thus, it is possible to independently manipulate and read out the data qubit and the auxiliary qubit without localized light irradiation.

[0070] As described above, the qubit array realized by combining nuclear spin qubits and optical transition qubits is a system that includes (1) data qubits with long coherence times and capable of high-speed operation, and (2) auxiliary qubits with long coherence times and capable of non-destructive measurement. Therefore, it is suitable for quantum error correction.

[0071] Up to this point, mainly, １７１ A nuclear spin qubit implemented using a Yb atom is a data qubit, and １７４ An example was described in which an optical transition qubit implemented using a Yb atom is an auxiliary qubit. However, in this embodiment, a fine-structure qubit may also be used instead of a nuclear spin qubit and an optical transition qubit.

[0072] <<Fine Structure Qubits>> In fine structure qubits, the state is described using transitions between two metastable states, and, similar to optical transition qubits, electron orbitals carry the information. Fine structure qubits can be implemented using either boson isotopes or fermion isotopes, but boson isotopes are preferred. This is because boson isotopes allow for the use of pairs of states whose energy is less affected by external conditions such as magnetic fields.

[0073] In the example of the Yb atom, １６８ Yb atom, １７０ Yb atom, １７２ Yb atom, １７４ Yb atom or １７６ Metastable state of a Yb atom ３ P ０ and metastable state ３ P ２ A transition between the states is used. １ P ０ > is state | 0 >, state |３ P ２ > is state |1>.

[0074] Microstructured qubits can utilize not only ytterbium atoms but also alkaline earth metals such as strontium atoms or calcium atoms. As for strontium atoms, ８４ Sr atom, ８６ Sr atom or ８８ Sr atoms can be used. Calcium atoms can be used as follows: ４０ Ca atom, ４２ Ca atom, ４４ Ca atom, ４６ Ca atom or ４８ Ca atoms can be used.

[0075] In microstructured qubits, readout is performed by transitioning an atom from one of two metastable states to the ground state, then irradiating the entire qubit array with probe light and detecting the fluorescence emitted from the atom in the ground state. Because the energy difference between the two metastable states is sufficiently large, it is possible to selectively transition an atom from one of the metastable states to the ground state. Only the atom that has been selectively returned to the ground state by this operation will emit fluorescence, while the atom remaining in the other metastable state will not. Therefore, it is not necessary to remove the qubit in state |1> when reading out a qubit in state |0>. Thus, non-destructive readout can be achieved even by using microstructured qubits.

[0076] Furthermore, while excitation of neutral atoms to the Rydberg state generally starts from a metastable state, in fine-structure qubits, alkaline earth atoms or alkaline earth-like atoms are already in a metastable state, making excitation to the Rydberg state relatively easy. This makes it possible to utilize the characteristic properties of Rydberg atoms to realize quantum gate operations beyond adjacent sites using, for example, long-range interactions on the μm scale.

[0077] Figure 8 illustrates the combinations of data qubits and auxiliary qubits when implemented with different atomic species. Figure 9 illustrates the combinations of data qubits and auxiliary qubits when implemented with different isotopes. In these figures, a column with at least one checkmark indicates that the corresponding combination is adoptable. A column with two to four checkmarks indicates that the corresponding combination is particularly favorably adoptable. A greater number of checkmarks is preferable. A blank column indicates that such a combination is outside the scope of this embodiment and will not be adopted.

[0078] Referring to Figure 8, when the data qubit and auxiliary qubit are implemented using different atomic species, a nuclear spin qubit or optical transition qubit with a long coherence time is preferred as the data qubit (see the column with two checkmarks). However, the data qubit may be a fine-structured qubit or a hyperfine-structured qubit using alkali atoms (see the column with one checkmark).

[0079] As mentioned above, nuclear spin qubits, optical transition qubits, and fine-structure qubits can all be readout nondestructively. Up to this point, we have shown an example in which optical transition qubits are used as auxiliary qubits, but the auxiliary qubits may also be nuclear spin qubits or fine-structure qubits.

[0080] Referring to Figure 9, when the data qubit and auxiliary qubit are implemented using different isotopes of the same atomic species, the data qubit may be any of the following: a hyperfine structure qubit, a nuclear spin qubit, an optical transition qubit, or a fine structure qubit. As with the case of different atomic species, a nuclear spin qubit or an optical transition qubit with a long coherence time is preferred as the data qubit (see the column with three or four checkmarks).

[0081] The auxiliary qubit may be a nuclear spin qubit, an optical transition qubit, or a fine-structure qubit, as long as it is not a hyperfine-structure qubit.

[0082] When the data qubit and auxiliary qubit are different isotopes, it is particularly preferable that the data qubit and auxiliary qubit are different types of qubits, as in this example where two types of qubits are implemented using two different isotopes of the Yb atom. This is represented in Figure 9 by writing one more check mark when the types of qubits are different compared to when the types of qubits are the same. By realizing a hybrid array containing multiple types of qubits, independent operation of the data qubit and auxiliary qubit can be easily achieved. In addition, there is the advantage of simplifying the device configuration of the quantum computer (avoiding excessive complexity of the light source and optical system of the optical tweezers array system).

[0083] <Processing Flow> Figure 10 is a flowchart showing an example of the processing procedure for the quantum computing method according to this embodiment. The processing shown in this flowchart is executed when predetermined conditions are met (for example, when the input device 73 receives a start operation from the user). Each step is typically implemented by software processing by the controller 7 (processor 71), but may also be implemented by hardware (electrical circuits) located inside the controller 7. Hereinafter, each step will be abbreviated as S.

[0084] The controller 7 first prepares a qubit array (S1). Next, the controller 7 uses the qubit array to execute a computation sequence that includes multiple gate operations, data qubit readout, and quantum error correction by readout of auxiliary qubits (S2).

[0085] Figure 11 is a flowchart showing an example of the processing procedure for preparing a qubit array (processing S1 in Figure 10). Figure 12 is a time chart showing an example of optical operations in qubit array preparation. Here again, １７１ Yb atom and １７４Yb atoms are used as data qubits and auxiliary qubits, respectively.

[0086] The horizontal axis in Figure 12 represents elapsed time. The vertical axis, from top to bottom, represents (1) Zeeman deceleration light (wavelength 399 nm), (2) first probe light (wavelength 399 nm), and (3) first atom ( １７１ (4) MOT light, LAC light and cooling light (all with wavelengths of 556 nm) for Yb atoms, and (5) second probe light (wavelength of 566 nm), and (6) second atom ( １７４ This figure shows the irradiation conditions of MOT light, LAC light, and cooling light (all with a wavelength of 556 nm) for Yb atoms. The numbers in the lower row of Figure 12 represent the irradiation time for each type of light.

[0087] Referring to Figures 11 and 12, in S101, the controller 7 controls the Zeeman decelerating light source 31 and the magneto-optical trap device 32 so that the atomic group 1 including the first atom 11 and the second atom 12 is captured (see times t0 to t2).

[0088] Figure 13 is an image of the captured atom group 1. It can be confirmed that the atom group 1 captured in the same magneto-optical trap contains two types of isotopes.

[0089] Referring again to Figures 11 and 12, in S102, the controller 7 controls the optical tweezers light source 33 so that an optical tweezers array (wavelength 532 nm) is generated. In this example, a 10x10 optical tweezers array (site spacing 5 μm) is generated.

[0090] In S103, the controller 7 controls the magneto-optical trap device 32 so that the magnetic field gradient gradually increases while irradiating with MOT light, thereby compressing the atom group 1 trapped in the magneto-optical trap to the position of the optical tweezers array (see times t2-t3). As a result, the atom group 1 is loaded into the optical tweezers array. At this stage, each site of the optical tweezers array is loaded with zero, one, or more atoms.

[0091] In S104, the controller 7 controls the photo-induced collision light source 34 to irradiate the atomic group 1 with LAC light (see times t3-t4). As a result, two atoms photo-associate to form a diatomic molecule.

[0092] Figure 14 is a diagram illustrating photosociation caused by irradiation with LAC light. In this embodiment, only the frequency corresponding to the molecular binding energy is used. １７４ Yb atom １ S ０ - ３ P １ By irradiating with LAC light red-detuned from the transition frequency, １７１ Yb atom and １７４ This process causes photoassociation with Yb atoms. This process is also called heteronuclear photoassociation. In addition, two １７４ Photo-association of Yb atoms with the same nucleus also occurs. Photo-induced collisions occur with the diatomic molecules thus generated, causing two atoms to be lost from each site in the optical tweezers array (two-body loss). Therefore, if an even number of atoms were initially loaded into a site, the number of atoms in that site will eventually become zero. On the other hand, if an odd number of atoms were initially loaded into a site, the number of atoms in that site will eventually become one. As a result, the number of atoms in each site becomes either zero or one. In other words, single-atom loading is achieved. However, since the number of atoms in approximately half of the sites becomes zero (atomic defects occur), dynamic tweezers are used to rearrange atoms in order to generate a lossless qubit array.

[0093] Returning to Figures 11 and 12, at S105, the controller 7 controls the first probe light source 4 to irradiate the entire qubit array with the first probe light, thereby capturing an image of the first atom 11. Subsequently, the controller 7 controls the second probe light source 5 to irradiate the entire qubit array with the second probe light, thereby capturing an image of the second atom 12 (see times t4-t5). By combining these two images, an image of the qubit array before atomic rearrangement is generated.

[0094] In S106, the controller 7 controls the cooling light source 35 to irradiate the entire qubit array with cooling light to suppress heating caused by the first probe light and the second probe light (see times t5-t6).

[0095] In S107, the controller 7 controls the optical tweezers light source 33 to rearrange the first atom 11 and the second atom 12 in the qubit array using a dynamic optical tweezers beam. Note that the atomic rearrangement operation is not shown in Figure 12.

[0096] In S108, the controller 7 controls the first probe light source 4 and the second probe light source 5 in the same manner as in the process of S105, thereby capturing an image of the qubit array after atomic rearrangement (see times t6-t7).

[0097] Figure 15 shows an example of an image of a qubit array before and after atomic rearrangement. In the figure, the first atom 11 ( １７１ The Yb atom is shown enclosed in a dotted circle, and the second atom 12 ( １７４ The Yb atom is shown without being enclosed in a circle.

[0098] Before atomic rearrangement, there are numerous empty sites (atomic deficiencies) that do not contain any atoms. Also, the first atom 11 and the second atom 12 are arranged irregularly (randomly). In contrast, after atomic rearrangement, the first atom 11 and the second atom 12 are arranged regularly without creating empty sites. Although Figure 15 shows an example of a checkerboard pattern, any arbitrary arrangement (such as a striped pattern) can be achieved.

[0099] The atomic survival rate in the qubit array after imaging using the first probe light and the second probe light was approximately 99% for both data qubits and auxiliary qubits. As mentioned above, the first probe light does not cause the loss of the second atom 12, nor does the second probe light cause the loss of the first atom 11. Therefore, even in a qubit array containing two types of isotopes according to this embodiment, an atomic survival rate equivalent to that of a qubit array containing only one of the isotopes can be achieved.

[0100] <Verification> <<Impact on data qubits>> Auxiliary qubits ( １７４ The readout of the Yb atom is a data qubit ( １７１ We will explain the verification results that show it does not affect the Yb atom.

[0101] Figure 16 shows an example of the coherence measurement results of a data qubit when an auxiliary qubit is read out. Figure 16 shows the Hahn-echo sequence measurement results for both cases: when an auxiliary qubit is read out (see black square) and when an auxiliary qubit is not read out (see white circle). The horizontal axis represents the scan time. The vertical axis represents the survival probability of the first atom 11 in the data qubit (probability of state |0>). The amplitude indicates the coherence of the data qubit.

[0102] As shown in Figure 16, the coherence measurement results of the data qubits were equivalent regardless of whether the auxiliary qubits were read out or not. Specifically, the ratio of the amplitude with auxiliary qubit readout to the amplitude without auxiliary qubit readout (contrast ratio) was 99.1 ± 1.8%. From this, it can be said that the readout of auxiliary qubits does not affect the auxiliary qubits themselves.

[0103] Figure 17 shows an example of the measurement results for the fidelity of an auxiliary qubit. Figure 17 also shows a histogram of the number of photons detected from the auxiliary qubit during irradiation with the second probe light. The horizontal axis represents the number of detected photons, and the vertical axis represents the frequency. The image in the upper right is a magnified view along the vertical axis.

[0104] The number of photons detected from an auxiliary qubit depends on the state of the auxiliary qubit. If the number of detected photons is greater than or equal to the threshold TH, the auxiliary qubit is in state |0>, and if the number of detected photons is less than the threshold TH, the auxiliary qubit is in state |1>. In Figure 17, the peaks for state |0> and state |1> are completely separated, so it is possible to clearly distinguish whether the auxiliary qubit is in state |0> or state |1>. In this verification, the read-through fidelity of the auxiliary qubit was 99.92%. This indicates that, according to this embodiment, it is possible to achieve read-through of the auxiliary qubit with high fidelity that satisfies the requirements of quantum error correction.

[0105] ≪Generation of Single Atomic Bits≫ Figure 18 shows an example of the verification results of single atomic bit generation using heteronuclear photoassociation processes. The horizontal axis represents the detuning frequency of LAC light. １７４ Yb atom ３ P １ This represents the frequency of LAC light near the resonance frequency. The top image in Figure 18 shows images of the qubit array when the detuning frequencies of the LAC light are -1.5 MHz, -0.5 MHz, and 0.5 MHz. The vertical axis of the middle figure represents the loading probability to the optical tweezers array for each isotope type (each site of the optical tweezers array is １７１ Ratio containing Yb atoms or １７４ This represents the ratio of Yb atoms. The vertical axis in the figure below represents the double occupancy rate of the optical tweezers array (each site is １７１ Yb atom and １７４ This represents the ratio of both Yb atoms.

[0106] When the detuning frequency of the LAC light is -1.5 MHz, the double occupancy is high, and the first atom 11 is located at many sites of the optical tweezers array. １７１ Yb atom) and second atom 12 ( １７４ Both Yb atoms were loaded. When the detuning frequency of the LAC light was 0.5 MHz, the doubling occupancy rate was almost 0, and the loading probability of the second atom 12 was also close to 0. That is, the second atom 12 was removed from almost all sites, leaving only the first atom 11.

[0107] In contrast, when the detuning frequency of the LAC light was -0.5 MHz, the double occupancy rate was low, close to zero, and both the loading probability of the first atom 11 and the loading probability of the second atom 12 were relatively high. That is, at each site, single-atom loading by either the first atom 11 or the second atom 12 was achieved. In the intermediate diagram of Figure 18, the decrease in the loading probability of the first atom 11 (dip) occurring around -0.5 MHz is due to the heteronuclear photoassociation process.

[0108] <Summary> As described above, in this embodiment, nuclear spin qubits, optical transition qubits, or microstructure qubits are used as auxiliary qubits in the qubit array. All three types of qubits can be read out nondestructively. Therefore, auxiliary qubits can be read out without causing atomic loss. In addition, the wavelength of the probe light (second wavelength) used to read out the auxiliary qubits does not affect the data qubits. As a result, the data qubits and auxiliary qubits can be operated and read out independently without localized light irradiation. Therefore, quantum error correction can be appropriately performed according to the quantum computer 100 and quantum computing method according to this embodiment.

[0109] Furthermore, in this embodiment, nuclear spin qubits or optical transition qubits are preferably used as data qubits in the qubit array. By using these types of qubits, a longer coherence time can be achieved compared to the alkali atom hyperfine structure qubits that are commonly used in the past.

[0110] Furthermore, by using different isotopes of the same atomic species, it is possible to simplify the system for generating the qubit array while improving the operability of each qubit constituting the qubit array, compared to using different atomic species. As a result, it becomes possible to realize a qubit array with any atomic arrangement in which, for example, a single atom is loaded at each site and there are no atomic vacancies at any site.

[0111] As illustrated above with specific examples, when using different isotopes of the same atomic species, a different type of qubit than the auxiliary qubit is preferably used as the data qubit. In other words, the qubit array according to this embodiment is a hybrid array containing multiple types of qubits. A hybrid array facilitates independent operation of the data qubit and the auxiliary qubit.

[0112] [Clause] Embodiments of this disclosure are described below as a Clause.

[0113] <Note 1> A quantum computer comprising: a plurality of neutral atoms including a plurality of first atoms and a plurality of second atoms of different types; an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of neutral atoms; a first probe light source configured to emit a first probe light for reading each of the plurality of first atoms as a data qubit; and a second probe light source configured to emit a second probe light for reading each of the plurality of second atoms as an auxiliary qubit, wherein the auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

[0114] <Note 2> The quantum computer described in Note 1, wherein the data qubit is a different type of qubit from the auxiliary qubit, among the hyperfine structure qubit, nuclear spin qubit, optical transition qubit, and fine structure qubit.

[0115] <Note 3> The quantum computer described in Note 2, wherein the data qubit is a different type of qubit from the auxiliary qubit, among nuclear spin qubits, optical transition qubits, and microstructure qubits.

[0116] <Note 4> The quantum computer described in Note 3, wherein the data qubit is a nuclear spin qubit, and the auxiliary qubit is an optical transition qubit or a microstructure qubit.

[0117] <Note 5> The quantum computer as described in Note 3, wherein the data qubit is an optical transition qubit, and the auxiliary qubit is a nuclear spin qubit or a microstructure qubit.

[0118] <Note 6> The quantum computer according to any one of Notes 1 to 5, wherein the plurality of first atoms are alkaline earth atoms or alkaline earth-like atoms, and the plurality of second atoms are alkaline earth atoms or alkaline earth-like atoms.

[0119] <Note 7> The quantum computer according to any one of Notes 1 to 5, wherein the plurality of first atoms and the plurality of second atoms are different isotopes of the same atomic species.

[0120] <Note 8> The quantum computer described in Note 7, wherein the plurality of first atoms and the plurality of second atoms are different isotopes of ytterbium atoms.

[0121] <Note 9> The quantum computer according to any one of Notes 1 to 5, wherein the plurality of first atoms and the plurality of second atoms are different atomic species.

[0122] <Note 10> The nuclear spin qubit is implemented using 171 ytterbium atoms, 173 ytterbium atoms, 87 strontium atoms, or 43 calcium atoms, and the optical transition qubit is implemented using 168 ytterbium atoms, 170 ytterbium atoms, 171 ytterbium atoms, 172 ytterbium atoms, 173 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 87 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 43 calcium atoms, 44 calcium atoms, 46 calcium atoms, or 48 calcium atoms, The quantum computer described in any one of the appendices 1 to 5, wherein the fine-structured qubit is implemented using 168 ytterbium atoms, 170 ytterbium atoms, 172 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 44 calcium atoms, or 46 calcium atoms.

[0123] <Note 11> The quantum computer according to any one of Notes 1 to 10, wherein the optical tweezers array system includes a photo-induced collision light source that emits light adjusted to cause two-body loss by photo-induced collision at each site of the optical tweezers array, and the quantum computer further includes a control device that controls the photo-induced collision light source to load a single atom into each site of the optical tweezers array using an heteronuclear photoassociation process between a first atom of the plurality of first atoms and a second atom of the plurality of second atoms.

[0124] <Note 12> A quantum computer comprising: a plurality of first atoms; a plurality of second atoms; an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of first atoms and the plurality of second atoms; a first probe light source configured to emit a first probe light for reading each of the plurality of first atoms as a data qubit; and a second probe light source configured to emit a second probe light for reading each of the plurality of second atoms as an auxiliary qubit, wherein the plurality of first atoms and the plurality of second atoms are two types of atoms, which are alkaline earth atoms and alkaline earth-like atoms, that are different atomic species or different isotopes from each other.

[0125] <Note 13> The quantum computer described in Note 12, wherein the plurality of first atoms and the plurality of second atoms are two different types of atoms selected from the group consisting of 168 ytterbium atoms, 170 ytterbium atoms, 171 ytterbium atoms, 172 ytterbium atoms, 173 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 87 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 43 calcium atoms, 44 calcium atoms, 46 calcium atoms, and 48 calcium atoms.

[0126] <Note 14> The quantum computer according to Note 13, wherein at least one of the plurality of first atoms and the plurality of second atoms functions as a nuclear spin qubit, and the at least one atom is selected from the group consisting of 171 ytterbium atoms, 173 ytterbium atoms, 87 strontium atoms, or 43 calcium atoms.

[0127] <Note 15> The quantum computer according to Note 13, wherein at least one of the plurality of first atoms and the plurality of second atoms functions as a fine structure qubit, and the at least one atom is selected from the group consisting of 168 ytterbium atoms, 170 ytterbium atoms, 172 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 44 calcium atoms, 46 calcium atoms, and 48 calcium atoms.

[0128] <Note 16> The quantum computer according to Note 12, wherein the plurality of first atoms and the plurality of second atoms are two different isotopes selected from the group consisting of 171-ytterbium atoms, 173-ytterbium atoms, and 174-ytterbium atoms.

[0129] <Note 17> A quantum computing method comprising the steps of: preparing an atomic array of multiple types of neutral atoms, including multiple first atoms and multiple second atoms of different types, using an optical tweezers array; irradiating the atomic array with a first probe light for reading each of the multiple first atoms as a data qubit; and irradiating the atomic array with a second probe light for reading each of the multiple second atoms as an auxiliary qubit, wherein the auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

[0130] <Note 18> The quantum computing method according to Note 17, wherein each of the plurality of first atoms and each of the plurality of second atoms are different isotopes of the same atomic species, and the preparation step includes loading a single atom into each site of the optical tweezers array using a heteronuclear photoassociation process between the first atom of the plurality of first atoms and the second atom of the plurality of second atoms.

[0131] The embodiments disclosed herein should be considered in all respects to be illustrative and not restrictive. The scope of this disclosure is indicated by the claims rather than by the description of the embodiments above, and all modifications within the meaning and scope of the claims are intended to be included.

[0132] 100 Quantum computer, 1 Neutral atom, 11 First atom, 12 Second atom, 2 Vacuum device, 3 Optical tweezers array system, 31 Zeeman decelerating light source, 32 Magneto-optical trap device, 33 Optical tweezers light source, 34 Photo-induced collision light source, 35 Cooling light source, 36 First objective lens, 37 Second objective lens, 381 Spatial light modulator, 382 Acousto-optic deflector, 391 Lens, 392 Dichroic mirror, 393 Mirror, 394 Dichroic mirror, 395 Lens, 396 Mirror, 397 Beam splitter, 4 First probe light source, 5 Second probe light source, 6 Imaging system, 61 Mirror, 62 Imaging lens, 63 Camera, 7 Controller, 71 Processor, 72 Memory, 721 System program, 722 Control program, 723 Calculation program, 73 Input device, 74 Output device, 75 Communication interface, 91 First atom, 92 Second atom.

Claims

1. A quantum computer comprising: a plurality of types of neutral atoms, including a plurality of first atoms and a plurality of second atoms of different types; an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of types of neutral atoms; a first probe light source configured to emit a first probe light for reading each of the plurality of first atoms as a data qubit; and a second probe light source configured to emit a second probe light for reading each of the plurality of second atoms as an auxiliary qubit, wherein the auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

2. The quantum computer according to claim 1, wherein the data qubit is a different type of qubit from the auxiliary qubit, among the hyperfine structure qubit, nuclear spin qubit, optical transition qubit, and fine structure qubit.

3. The quantum computer according to claim 2, wherein the data qubit is a different type of qubit from the auxiliary qubit, among nuclear spin qubits, optical transition qubits, and microstructure qubits.

4. The quantum computer according to claim 3, wherein the data qubit is a nuclear spin qubit, and the auxiliary qubit is an optical transition qubit or a microstructure qubit.

5. The quantum computer according to claim 3, wherein the data qubit is an optical transition qubit, and the auxiliary qubit is a nuclear spin qubit or a microstructure qubit.

6. The quantum computer according to any one of claims 1 to 5, wherein the plurality of first atoms are alkaline earth atoms or alkaline earth-like atoms, and the plurality of second atoms are alkaline earth atoms or alkaline earth-like atoms.

7. The quantum computer according to claim 6, wherein the plurality of first atoms and the plurality of second atoms are different isotopes of the same atomic species.

8. The quantum computer according to claim 7, wherein the plurality of first atoms and the plurality of second atoms are different isotopes of a ytterbium atom.

9. The quantum computer according to claim 6, wherein the plurality of first atoms and the plurality of second atoms are different atomic species.

10. The nuclear spin qubit is implemented using 171 ytterbium atoms, 173 ytterbium atoms, 87 strontium atoms, or 43 calcium atoms, and the optical transition qubit is implemented using 168 ytterbium atoms, 170 ytterbium atoms, 171 ytterbium atoms, 172 ytterbium atoms, 173 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 87 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 43 calcium atoms, 44 calcium atoms, 46 calcium atoms, or 48 calcium atoms, The quantum computer according to any one of claims 1 to 5, wherein the fine-structured qubit is implemented using 168 ytterbium atoms, 170 ytterbium atoms, 172 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 44 calcium atoms, or 46 calcium atoms.

11. The quantum computer according to any one of claims 1 to 5, wherein the optical tweezers array system includes a photo-induced collision light source that emits light tuned to cause two-body loss by photo-induced collision at each site of the optical tweezers array, and the quantum computer further includes a control device that controls the photo-induced collision light source to load a single atom into each site of the optical tweezers array using an heteronuclear photoassociation process between a first atom of a plurality of first atoms and a second atom of a plurality of second atoms.

12. A quantum computer comprising: a plurality of first atoms; a plurality of second atoms; an optical tweezers array system configured to generate an optical tweezers array for arranging the plurality of first atoms and the plurality of second atoms; a first probe light source configured to emit first probe light for reading each of the plurality of first atoms as a data qubit; and a second probe light source configured to emit second probe light for reading each of the plurality of second atoms as an auxiliary qubit, wherein the plurality of first atoms and the plurality of second atoms are two types of atoms, which are alkaline earth atoms and alkaline earth-like atoms, that are different atomic species or different isotopes from each other.

13. The quantum computer according to claim 12, wherein the plurality of first atoms and the plurality of second atoms are two different types of atoms selected from the group consisting of 168 ytterbium atoms, 170 ytterbium atoms, 171 ytterbium atoms, 172 ytterbium atoms, 173 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 87 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 43 calcium atoms, 44 calcium atoms, 46 calcium atoms, and 48 calcium atoms.

14. The quantum computer according to claim 13, wherein at least one of the plurality of first atoms and the plurality of second atoms functions as a nuclear spin qubit, and the at least one atom is selected from the group consisting of 171 ytterbium atoms, 173 ytterbium atoms, 87 strontium atoms, or 43 calcium atoms.

15. The quantum computer according to claim 13, wherein at least one of the plurality of first atoms and the plurality of second atoms functions as a fine structure qubit, and the at least one atom is selected from the group consisting of 168 ytterbium atoms, 170 ytterbium atoms, 172 ytterbium atoms, 174 ytterbium atoms, 176 ytterbium atoms, 84 strontium atoms, 86 strontium atoms, 88 strontium atoms, 40 calcium atoms, 42 calcium atoms, 44 calcium atoms, 46 calcium atoms, and 48 calcium atoms.

16. The quantum computer according to claim 12, wherein the plurality of first atoms and the plurality of second atoms are two different isotopes selected from the group consisting of 171-ytterbium atoms, 173-ytterbium atoms and 174-ytterbium atoms.

17. A quantum computing method comprising the steps of: preparing an atomic array of multiple types of neutral atoms, including multiple first atoms and multiple second atoms of different types, using an optical tweezers array; irradiating the atomic array with a first probe light for reading each of the multiple first atoms as a data qubit; and irradiating the atomic array with a second probe light for reading each of the multiple second atoms as an auxiliary qubit, wherein the auxiliary qubit is a nuclear spin qubit, an optical transition qubit, or a fine structure qubit.

18. The quantum computing method according to claim 17, wherein each of the plurality of first atoms and each of the plurality of second atoms are different isotopes of the same atomic species, and the preparation step includes loading a single atom into each site of the optical tweezers array using an heteronuclear photoassociation process between a first atom of the plurality of first atoms and a second atom of the plurality of second atoms.

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