Modular interconnection between neutral atom quantum processors

Abstract

A device for modular interconnection between quantum processors is provided. The device includes an optical cavity configured to simultaneously collect photons from two transitions with opposite circular polarizations. The optical cavity includes a plurality of mirrors with a twisted, non-planar toroidal geometry configured to realize two non-degenerate co-propagation modes with opposite circular polarizations.

Description

[0001] Cross-references to related applications

[0002] This application claims the benefit and priority of U.S. Provisional Patent Application Serial No. 63 / 618,134, filed January 5, 2024, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The subject of this disclosure generally relates to the field of quantum computing, and more specifically to a device for modular interconnection between quantum processors. Background Technology

[0004] Developing a large-scale fault-tolerant quantum computer capable of solving problems that classical methods struggle with is expected to require millions of qubits. In many physical computing architectures, it is difficult to imagine scaling a single device to this number of qubits due to various limitations, including cryogenic cooling power, wiring density, or laser power.

[0005] However, a core challenge in realizing modular quantum systems is achieving inter-module quantum links with sufficient bandwidth and fidelity. The fundamental building block of modular computers is the Bell pair between physical qubits in two modules, which can be used as a resource for executing remote physical or logic gates via teleportation. Spin-photon entanglement in neutral atoms and trapped ions has been used to generate Bell pairs on meter-scale fiber optic links, where the rate is... Furthermore, the fidelity is 0.94. In superconducting qubits, microwave photons have been used to entangle qubits in the same cryostat and in two cryostats separated by a 30-meter cold link. Entangling qubits between two qubits via a room-temperature link is an open challenge.

[0006] Therefore, there is still a need for improvement. Summary of the Invention

[0007] According to various aspects of this disclosure, a device for modular interconnection between quantum processors includes an optical cavity configured to simultaneously collect photons from two transitions having opposite circular polarizations. The optical cavity includes a plurality of mirrors in a twisted, non-planar toroidal geometry configured to realize two non-degenerate co-propagation modes with opposite circular polarizations.

[0008] In one aspect of this disclosure, the energy split between two non-degenerate co-propagation modes can be tuned to match the spacing between atomic energy levels with opposite spins, allowing the atom to simultaneously emit photons of two polarizations into the cavity, thereby generating entanglement between spin and polarization states.

[0009] In another aspect of this disclosure, the atom can be 171Yb. The optical cavity is tuned to match the... 3 P0 F=1 / 2 mF=+ / -½ state to 3 D1 F=3 / 2 mF=+ / - 3 / 2 state transition resonance.

[0010] According to various aspects of this disclosure, a system includes means for modular interconnection between quantum processors. The means includes: an optical cavity configured to simultaneously collect photons from two transitions having opposite circular polarizations, the optical cavity including a plurality of mirrors in a twisted, non-planar toroidal geometry configured to realize two non-degenerate co-propagation modes having opposite circular polarizations; and an array of optical tweezers configured to be transferred into the optical cavity using steerable mirrors, the array of optical tweezers including N > 1 sites.

[0011] In a further aspect of this disclosure, the system may further include an optical fiber having a first end operatively coupled to an optical cavity, such that the first end of the optical fiber is configured to receive photons emitted by atoms.

[0012] In a further aspect of this disclosure, the system may further include a central router operatively coupled to a second end of an optical fiber, the central router being configured to receive photons from the optical fiber.

[0013] In another aspect of this disclosure, photons from an optical fiber can be directed toward a beam splitter in a central router.

[0014] In another aspect of this disclosure, the system may further include a second optical fiber incident on the beam splitter from the second module, wherein a central router is reconfigured to direct photons from different module pairs toward each beam splitter in the beam splitter array.

[0015] According to various aspects of this disclosure, a method for connecting a quantum computing module based on neutral atom qubits includes: initializing an optical tweezers array comprising N > 1 sites, each site having a single atom, outside an optical cavity of a first quantum computing module; the optical cavity comprising a plurality of mirrors in a twisted ring configuration configured to realize two non-degenerate co-propagation modes having opposite circular polarizations; one of the mirrors being configured as an output coupler; and energy splitting between the two non-degenerate co-propagation modes being tuned to match the spacing between atomic energy levels of opposite spins, such that the atoms simultaneously emit photons of both polarizations into the optical cavity, thereby generating entanglement between the spin state and each polarization; transferring the optical tweezers array into the optical cavity using a steerable mirror or an acousto-optic deflector; and optically pumping the optical tweezers array to... 1In a single spin state within the ground state S0, F=1 / 2; and in a superposition of spin states by simultaneously performing single qubit rotations on all qubits on the optical tweezers array.

[0016] In a further aspect of this disclosure, atoms can be 171 Yb. This method may further include allowing the first atom to use a two-photon optical transition from 1 The ground state S0 F=1 / 2 is excited to 3 D1 F=3 / 2 excited state, in the state of 3 In the superposition of states D1 F=3 / 2 mF=+ / - 3 / 2.

[0017] In a further aspect of this disclosure, the method may further include: allowing atoms to decay by emitting photons into an optical cavity, the optical cavity being tuned to interact with the light emitted from the source. 3 P0 F=1 / 2 mF=+ / - ½ state to 3 The D1 F=3 / 2 mF=+ / - 3 / 2 state transition resonance, in the state of 3 An entangled state is generated between the spin of the atom in the P0 state and the polarization of the photon; the photon is collected into an optical fiber and the image is sent to a central router; and interference occurs at the beam splitter with a photon from the second quantum computing module. The coincidence detection of the two photons indicates that an entangled state has been generated between the atoms in the first and second quantum computing modules.

[0018] In another aspect of this disclosure, the method may further include reinitializing at least two atoms with failed entanglement back to their original state via optical pumping. 1 S0 ground state.

[0019] In another aspect of this disclosure, the method may further include: using an acousto-optic deflector or a scannable mirror to move an array of optical tweezers out of the optical cavity and into the computation region; and moving another array of atomic optical tweezers into the optical cavity.

[0020] In a further aspect of this disclosure, information about the arrival time of the detected photon can be used to infer the error probability on the resulting Bell pair, and this information is used in the computation of quantum error correction code to perform estimation of the logical quantum bit state.

[0021] In a further aspect of this disclosure, the method may further include controlling crosstalk and reabsorption of photons within the optical cavity by removing atoms that have not undergone entanglement attempts at any point in time from the optical cavity in conjunction with the resonance of the optical cavity.

[0022] In another aspect of this disclosure, the atoms can be removed from the resonance using the AC Stark displacement of a focused beam array.

[0023] In another aspect of this disclosure, the wavelength of the focused beam array can be selected such that... 3 P0 to 3 The transition energy of D1 is significantly shifted compared to the coupling between the atom and the optical cavity, to prevent photons emitted into the optical cavity from being absorbed by other atoms.

[0024] In a further aspect of this disclosure, the wavelength of the focused beam array can be selected such that... 3 The D1 state is used to transfer atoms from 1 S0 is excited to 3 The Rabi frequency of the two-photon transition of P1 shifts significantly to control the state at which the transition occurs. 1 Which atom in the S0 state is excited to...? 3 In the D1 state, an attempt is made to initiate spin-photon entanglement.

[0025] In a further aspect of this disclosure, the method may further include applying one or more optical displacements to the excited atoms while the excited atoms are still emitting photons, to suppress further photon emission into the optical cavity.

[0026] In a further aspect of this disclosure, applying one or more optical shifts can be done when the atom has completely decayed to... 3 It occurs before the P0 state, at a time when there is no photon excitation in the optical cavity.

[0027] Further details and aspects of exemplary embodiments of the present disclosure are described in more detail below with reference to the accompanying drawings. Attached Figure Description

[0028] The features and advantages of this disclosure will be better understood by referring to the following detailed description of illustrative embodiments that utilize the principles of this disclosure, along with the accompanying drawings:

[0029] Figure 1 This is a block diagram illustrating the modular interconnection between neutral atom quantum processors of a quantum computer, according to various aspects of this disclosure;

[0030] Figure 2 This is a block diagram illustrating various aspects of a quantum computer based on this disclosure;

[0031] Figure 3 Based on the various aspects presented in this disclosure Figure 1 A diagram of the optical cavity of the system;

[0032] Figure 4 Based on the various aspects presented in this disclosure Figure 1 A diagram illustrating the operation of the system;

[0033] Figure 5 Based on the various aspects presented in this disclosure Figure 1 A diagram illustrating the operation of the system;

[0034] Figure 6 Based on the various aspects presented in this disclosure Figure 1 A diagram illustrating the temporal entanglement sequence of the system;

[0035] Figure 7 Based on the various aspects presented in this disclosure Figure 3 A diagram of the atomic array inside the cavity;

[0036] Figure 8 This is a set of graphs illustrating the cavity output photon rate, photon extraction efficiency, and Bell pair generation rate according to various aspects of this disclosure; and

[0037] Figure 9 This is a flowchart illustrating a method for connecting a quantum computing module based on neutral atom qubits, according to various aspects of this disclosure. Detailed Implementation

[0038] The subject of this disclosure generally relates to the field of quantum computing, and more specifically to modular interconnects between quantum processors.

[0039] Although this disclosure will be described by way of specific examples, those skilled in the art will readily understand that various modifications, rearrangements and substitutions can be made without departing from the spirit of this disclosure.

[0040] To facilitate understanding of the principles of this disclosure, reference will now be made to the exemplary embodiments shown in the accompanying drawings, and these embodiments will be described using specific language. However, it should be understood that this is not intended to limit the scope of this disclosure. Any changes and further modifications to the novel features shown herein, as well as any additional applications of the principles of this disclosure as illustrated herein, will be considered within the scope of this disclosure and will occur to those skilled in the art and those who possess this disclosure.

[0041] The system and method disclosed in this paper realize long-range spin entanglement between neutral atom qubits in an optical tweezers array. 171 Yb atoms are considered as qubits, which have been used to demonstrate high-fidelity entanglement gates, non-destructive and intermediate circuit readout, and have a pathway to achieve efficient fault-tolerant error correction using erase transitions. By placing N > 100 atoms within a single optical cavity (a twisted ring resonator) using an array of optical tweezers and controlling their interaction with the cavity using only local optical displacement, this disclosure predicts, for physically plausible parameters, a long-range Bell pair generation rate of [missing value]. Furthermore, the fidelity F > 0.998. This rate is several orders of magnitude higher than previously demonstrated or proposed long-range entanglement methods for atomic qubits. Entanglement uses 1389 nm photons in a single-mode fiber to distribute between modules, allowing links over distances of several kilometers without degradation.

[0042] refer to Figure 1 This illustrates a neutral atom quantum computer 200 for connecting neutral atom-based qubits. Figure 2 The system 100 comprises quantum computing modules 110 and 120 of the quantum computer 200. The system 100 generally includes the quantum computing modules 110 and 120 of the quantum computer 200. Figure 2 ) and optical tweezers array 102 ( Figure 3 The optical tweezers array includes N > 1 sites, each with a single atom. Each of the quantum computing modules 110 and 120 includes an optical cavity 300. Figure 3 ).

[0043] System 100 addresses the problem of slow entanglement generation in conventional systems, which require placing one atom at a time in the optical cavity to generate spin-photon entanglement. System 100 solves this problem by simultaneously placing many atoms in the cavity and selectively coupling one atom at a time by shifting the transition frequencies of the remaining atoms, which can be done rapidly.

[0044] An optical tweezers array 102 is located outside the optical cavity 300. The optical tweezers array 102 is configured to be transferred into the optical cavity 300 using a steerable mirror, and the optical tweezers array 102 includes N > 1 sites.

[0045] Optical cavity 300 includes a plurality of mirrors 304 (e.g., four mirrors) arranged in a twisted or non-planar annular shape, configured to realize two non-degenerate co-propagation modes with opposite circular polarizations. Optical cavity 300 is configured to simultaneously collect photons from two transitions with opposite circular polarizations. One of the mirrors 304 can be configured as an output coupler. The energy split between the two non-degenerate co-propagation modes is tuned to match the spacing between atomic energy levels with opposite spins, allowing the atoms to simultaneously emit photons of both polarizations into the optical cavity, thereby generating entanglement between the spin state and each polarization.

[0046] refer to Figure 2A diagram of a quantum computer 200 is shown. Each module 110, 120 of the quantum computer 200 can be housed in a separate vacuum system 114 and contains an optical cavity for generating spin-photon entanglement. The generated photons are entangled with qubit states in a polarization basis. After the photons leave the optical cavity, they are coupled into an optical fiber and sent to a central reconfigurable router 112 and a detector array. The coincidence detection of two photons with different polarizations announces the generation of a Bell state between qubits in a remote module. The central router 112 is operatively coupled to a second end of the optical fiber and is configured to receive photons from the fiber. The central router 112 is used to converge photons from two different modules. The central router 112 can be reconfigured to converge photons from any pair of modules onto a beamsplitter. The central router 112 may include a second optical fiber incident on the beamsplitter from the second module. The central router 112 is reconfigured to direct photons from different module pairs toward each beamsplitter in the beamsplitter array.

[0047] refer to Figure 3 The diagram illustrates the design of an exemplary optical cavity 300. The optical cavity 300 includes four mirrors 304 arranged in a twisted annular shape between two lenses 302 and 306. The large spacing between the mirrors 304 and the atoms eliminates unwanted atom-surface interactions and provides space for the optical tweezers 102 (…). Figure 1 Imaging and gate beams provide ample optical pathways. The radius of curvature of the mirrors is chosen to provide [optical information] at the location of the atoms. The pattern waist, thus producing The peak atom-cavity coupling intensity, and provides space for N = 204 atoms, where ( Figure 7 The round-trip length is L = 6.96 cm, corresponding to a free spectral range of 4.3 GHz, and the cavity decay rate κ is selected by choosing the reflectivity of the output coupler mirror (the other mirrors have R = 1). The output coupler mirror is typically partially transmissive, allowing a small portion of light to escape from the cavity. This is typically the mirror from which light exits.

[0048] Choose the twist angle to propagate the co-propagation. and The mode is split at approximately 140 MHz to simultaneously match from a 100 Gauss bias field. and arrive 3 The transition of D1. Different twist angles can be selected to achieve different splits to match the transition frequencies under different magnetic field values.

[0049] The optical cavity 300 within each module 110, 120 is a twisted toroidal cavity, capable of achieving robustly aligned, small-beam-waist (e.g., approximately 10 micrometers), spatially uniform atom-cavity coupling (i.e., no standing waves), and non-degenerate modes with opposite circular polarizations to simultaneously couple to two Zeeman split transitions and generate spin-polarization entanglement. This doubles the entanglement generation rate compared to time-box entanglement when coupled to a single transition, and avoids storing entanglement in a superposition of electronic energy levels that might be more sensitive to differential optical shifts or magnetic field fluctuations. In all respects, when the atom is 171 At Yb, the optical cavity can be tuned to match the... 3 P0 F=1 / 2 mF=+ / - ½ state to 3 D1 F=3 / 2 mF=+ / -3 / 2 state transition resonance.

[0050] The disclosed optical cavity 300 solves the problems of traditional standing wave cavities by eliminating rapid spatial changes in the atom-cavity coupling strength. Four non-planar mirrors are each positioned at an angle.

[0051] refer to Figure 4 This illustrates a display of a device with a tweezers array 102. Figure 1 The flowchart shows the system's operation. At operation 410, the atomic array 401 is initialized in the loading region and then transferred to the optical cavity 300. At operation 420, once inside, the entire array 401... 1 S0 ground state The internal state is initialized to a superposition state. The first atom in the array is excited to 6s5d. 3 Superposition state in D1 manifold This superposition state is achieved by emitting a signal into the cavity that has… or Polarized 1389 nm photons decay to 3 Quantum bit states in P0 manifold ( Figure 5 This produces spin-photon entangled states. Through two modules 110 and 120 ( Figure 1 Excitation is performed synchronously in the process, and the emitted photons will arrive at the detector simultaneously. When two photons with opposite polarizations are detected, the entangled state of the two qubits is achieved. It was declared.

[0052] This process is repeated sequentially for each atom in array 401, having The delay ensures that photon wave packets do not overlap. After all atoms are excited once, the process can be repeated m times, where m is between 5 and 10, to improve the entanglement fraction. Between repetitions, atoms that were not successfully entangled are reinitialized to their original state. .

[0053] After generating a sufficient number of Bell pairs, at operation 430, the array is removed from the cavity (i.e., moved into the computational region where it can be consumed to perform remote gate operations via teleportation) and replaced by a new array to continue generating more Bell pairs. This is achieved by reducing the time cost of moving atoms (t...). 移动 ≈ 100 μs) is distributed across multiple repetitions of the entangled sequence. Figure 6 The average spin-photon entanglement attempt rate approaches the maximum allowed by the cavity, 1 / t. 纠缠 The number of atoms required in the cavity to saturate this rate is... . 3 Local addressing optical displacement in D1 state prevents it from being in the already in 3 The atoms of P0 reabsorb photons and provide access to the source. 1 S0 to 3 Local control of D1 excitation.

[0054] refer to Figure 5 , showed 171 The energy diagram of the relevant atomic energy levels in Yb. The quantum bit states used for calculation are... 3 Po manifold.

[0055] Used to generate spin-photon entangled states The process is as follows Figure 8 As shown. The array was fabricated via optical pumping. In, and then prepared using single-qubit rotation in Afterwards, a short light pulse is used to excite the superposition state to... 3 D1 (via) 3 P1 intermediate state). When The photon emission rate outside the cavity does not decay exponentially, but exhibits periodic oscillations with a frequency close to g. Figure 8 Over 90% of the decays occur within the first cycle of this oscillation, but if the next atom is immediately excited, the residual population in the cavity can lead to errors. Therefore, when minimizing the cavity photon population, in The strong light was suddenly shifted. Apply to 3 The D1 state. This traps the residual excitation within the atom, causing it to decay into a free-space mode, and allows the next atom to be immediately excited to the D1 state. 3 D1, thus providing more than a 2x speed improvement. The optical shift remains on for the remainder of the sequence to prevent atoms from absorbing cavity photons from subsequent excitation rounds (for this, a larger optical shift is required). (This is preferred). After attempting to excite all N atoms, the unentangled atoms can be pumped back to... The entanglement process is repeated until the required number of Bell pairs are generated.

[0056] refer to Figure 8 A set of graphs showing the output photon rate, photon extraction efficiency, and Bell's ratio generation rate of the display cavity are presented. The photon extraction efficiency is shown as... The function, when When the maximum value is reached (Corresponding to a cavity fineness F = 2070). This does not achieve the maximum possible efficiency. ,in It is synergy, because when When the cavity is smaller, its spectral width becomes narrower than that of the emitted photons. Adiabatic preparation of shaped photon pulses can always be achieved. However, this comes at the cost of a lower emission rate and significant additional experimental complexity. Each excited atom has a probability of successfully generating a long-range Bell pair. .use Figure 6 The average Bell pair rate of the sequence is:

[0057]

[0058] in It is the first The number of entanglement attempts in a round, and N1 = N. After one round (m = 1), the rate is ,for The number of wheels increased to This is 88% of the maximum speed allowed by the cavity. = This indicates the validity of the reuse.

[0059] Next, this disclosure considers errors that affect spin-spin entanglement fidelity. Previous experimental studies of declared entanglement based on coincidence detection have identified errors originating from atomic coherence, single-qubit spin fidelity, polarization mixing, and imperfect mode overlap at the detector.

[0060] 171 The excellent coherence of Yb nuclear spin qubits and the high-fidelity single-qubit operation largely mitigate the first two effects. Due to its low sensitivity to magnetic field noise and the absence of differential optical shift, it has been proven that... 1 S0 or 3 Pure nuclear spin qubits in P0 exist without dynamic decoupling (i.e., In the case of [the specific condition], there is a coherence time of several seconds. In typical optical tweezers, the metastable lifetime is 3 s, resulting in [a specific time] per [time]. decay to 1 The probability of S0 is Or, under the condition of m = 5 sequence repetitions and N = 204 atoms, Furthermore, metastable decay errors can be converted into erase errors, thereby minimizing their impact on logical information. 3 The D1 state is more sensitive to magnetic fields, but is only populated for about 1 μs during entanglement generation. (Regarding...) 1 S0 and 3 The single-qubit gates of P0 qubits have all been shown to have fidelity exceeding 0.999. The polarization orthogonality of the emitted photons is ensured by the cavity's mode structure, and extremely high spatial mode overlap can be achieved by using optical fibers or integrated photonic beamsplitters with extremely low loss at telecommunication wavelengths.

[0061] This disclosure now assesses the sources of error specific to this embodiment. The first is the slight distinguishability of photon wave packets from the two cavities due to variations in the atom-cavity coupling strength or Doppler shift. Given two atoms in the two cavities, their coupling strength has a fractional difference. The resulting discriminability leads to errors. This makes it necessary Only then can it be achieved The |RMS change of g below this level requires matching the cavity waist at the 5% level and placing the atom at the cavity center. Inside (and) Figure 7 (Layout compatibility in g). This static inhomogeneity can be mitigated by misaligning atoms in a cavity or by selecting matching pairs of atoms to become entangled. Unknown variations in g can be caused by alignment displacement between the tweezer array and the cavity or by the thermal motion of atoms. To achieve This disclosure requires (By the means that there are no standing waves in the cavity), while Thermal motion at that location corresponds to .

[0062] Considering the traveling wave modes within the cavity, distinguishability errors can also be caused by Doppler displacement. Error probability. and Proportional, of which It is a cavity wave vector. Here, is the Boltzmann constant, T is the atomic temperature, and m is the mass of the atom. Through numerical simulations, this disclosure discovers... The typical temperature for Yb atoms is... (No ground-state cooling), corresponding to .

[0063] Next, consider decaying back during the excitation pulse. 1 S0 causes the initial spin superposition state to collapse, but if the atom is re-excited, it can still cause photons to be emitted into the cavity. 3 The D1 state decays to a branching ratio of 0.35. 3P1, and 3 P1 with The rate of decay to 1 S0. Therefore, during a duration of decay to during the excitation pulse 1 The probability of S0 is The probability that an atom is re-excited and causes an error is... .for The magnitude of existence is The additional decay probability, where Δ3 is the two-photon excited laser relative to 3 The detuning of P1. However, by using a large detuning Δ3 > 1 GHz, it can be suppressed to the following.

[0064] Commercially available superconducting nanowire single-photon detectors (SNSPDs) have dark count rates. And a quantum efficiency of >90%, corresponding to an error probability of However, it has been proven that it is achievable. The techniques include cold filtering and coupling the detector to a single-mode waveguide, which in principle allows .

[0065] Crosstalk errors caused by the presence of multiple atoms within the cavity take two forms: residual photons leaking into the next window at the end of an entanglement attempt, and photons already in the cavity... 3 Atoms in P0 can absorb photons if they are not optically displaced sufficiently away from the cavity resonance. If the atom-cavity coupling is precisely known, residual photon errors are significantly suppressed by optical displacement, provided that the optical displacement is instantaneously turned on at the moment the cavity population is zero. However, unknown variations in g make such precise timing impossible. (Used in...) Uncertainty caused by the motion of thermal atoms They discovered that it has a light displacement of Lower limit of time .

[0066] After a successful attempt at entanglement, it is now in a state of... 3 The atoms of P0 can absorb photons from the cavity in subsequent rounds of the protocol. This error is also suppressed by optical shift, such as... However, because the error occurs on already entangled atoms, the average generated Bell pairs undergo... Subsequent rounds amplified its effect. When N = 204 and m = 5, this disclosure, through numerical calculations, found... Achieve average error need From a geometric perspective, the probability of reabsorption through free space is relatively small, but it can be suppressed to a lower level by intentionally adding disorder to the light displacement: A 10% change corresponds to 100 linewidths of an atomic transition.

[0067] It should be noted that when in 3 D1 to 6s8p 3 When the P1 transition approaches resonant operation, it is possible that the optically shifted beam requires only a moderate amount of laser power, because... 3 The D1 state is unpopulated at the frequency shift site and is therefore insensitive to scattering errors. At 1 GHz detuning, each atom The laser power is sufficient to generate The optical displacement.

[0068] In the context of quantum error correction, the details of the error model can significantly affect the overhead required to achieve a given logic error rate. For example, it has been shown that biasing a single type of Pauli error, or providing information about the location of the error in the form of erasure or soft information, can reduce the logic error rate by several orders of magnitude. While many quantum operations are characterized by their average fidelity, the timing of photon detection events provides successive information about the error probability for each Bell pair. Soft information typically includes probabilistic data about quantum states, which includes information describing the likelihood or confidence of the state being in a particular value rather than a deterministic outcome. The disclosed system 100 provides the benefit of providing this soft information, which can be used to determine the type of error and improve the error rate based on it. For example, the type of error (e.g., the error rate for a given Bell pair) can be determined based on tuning information. The tuning information can then be used to guide the design of fault-tolerant gates or iteratively improve the error correction process.

[0069] For example, at a known time In the event of coincidence photon detection, what is the probability that the obtained atomic state is in a correct Bell state or has Pauli (X, Y, Z) or leakage error on one or two qubits? 171 The qubit manifold in Yb has only two levels, and leakage error refers to the fact that atoms are not in a proper state. 3 The case of P0.

[0070] For example, due to the change in the atom-cavity coupling strength The photon distinguishability resulting from (corresponding to the number of atoms N = 204) may lead to errors. These errors are purely Pauli Z errors: distinguishability affects the phase of the resulting Bell pair but does not affect the correlation between photon polarization and spin state (i.e., does not cause X errors) or leakage. When photons are detected at almost the same time, the error probability is strongly suppressed because there is less path information. The prior probability distribution using photon detection time is shown. This can be converted into a probability distribution of the error rate. . The meaning is as follows: It gives the generated Bell state with an error rate of 100%. The probability is determined using all available information about the photon detection timing. Although the average error rate is... However, more than half of the Bell pairs had an error rate of less than [percentage missing]. This information can be used to decode logic errors more effectively because it approximates erase errors.

[0071] A similar description can be applied to errors caused by Doppler shift. As for photon detection time... The error probability is a function of the function. Since the Doppler shift only affects the distinguishability of the photon wave packet, it only leads to the Z error.

[0072] During the excitation pulse via 3 The error arising from P1 decay can be understood as a Z-basis measurement of the spin prior to spin-photon entanglement, and is also purely Z-biased. However, photon detection timing does not reveal any information about the probability of this error, and therefore it is the same for all Bell pairs.

[0073] Dark counting leads to false announcements unrelated to atomic states and can introduce any Pauli error or leakage. Error probability. It depends slightly on the detection time and the corresponding cumulative distribution functions of Z, X and leakage errors.

[0074] For example, errors may arise from the absorption of photons by atoms already in a Bell pair and from atoms moving away from the Bell pair. 3 The errors occur due to P0 decay. Since both errors occur after a successful announcement, they are independent of any photon detection timing mode. However, Bell pairs generated in earlier rounds have a greater chance of experiencing errors compared to Bell pairs generated in later rounds. The number of entangled rounds N following the generation of a successful Bell pair is used. r Given the known probability distribution, generate the probability distributions of Z, X, and leakage error. For those already in... 3 Error caused by atomic absorption of photons in P0 Because the atoms are far from the cavity and detuned, they are excited to 3 All m in D1 F The probabilities of the levels are roughly equal, therefore the probabilities of X, Z, and leakage error are also roughly equal. For atoms from... 3 The decay of P0, error By definition, it's purely a leak.

[0075] In summary, these results demonstrate that information regarding photon detection timing can reveal a significant subset of atoms with error rates that differ from the average error rate by approximately 5 to 10 times. Regrouping atoms with different error rates, or using this information during decoding, can lead to significant improvements in logic error rates and corresponding reductions in overhead.

[0076] System 100 offers the benefit of generating entanglement in parallel with computation using metastable qubits in the vicinity region without the need for separate magnetic field control. Local addressing requirements are minimal, consisting of only a single switchable optical shift at each site, and it is compatible with recently demonstrated scalable modulators.

[0077] System 100 enables the conversion of physical Bell pairs into logical Bell pairs for distributed fault-tolerant computation. Many previous studies have considered modular quantum computing in schemes where modules are small and a single logical qubit spans multiple modules. While it has been shown that inter-module links have a high error threshold of 10%, long-range Bell pairs are consumed at a high rate, merely to maintain logical information against idle errors. In the case of neutral atom quantum computing, this disclosure envisions each module having… A module of 10,000 qubits, based on a proven array of hundreds of qubits and an underlying optical component extending to 10,000 sites. The predictable error rate for all physical operations is less than [missing information]. In this case, using standard surface codes, with 10 per logical qubit. 3 It can be achieved with the overhead of a physical qubit. The logic error rate. This can be further reduced by an order of magnitude by using qubits with engineered noise or efficient block code. Therefore, for each module N... L One hundred logical qubits are realistically feasible. In this scheme, long-range Bell pairs are not consumed for correcting storage and computational errors within each module, but are purely used to perform logical operations between modules. For surface codes with a distance of d, gate operations between long-range logical qubits can be implemented via lattice manipulation, consuming d... 2 A physical Bell pair.

[0078] Alternatively, the same number of Bell pairs can be converted into logically entangled states by locally measuring the stabilizers, and then the logic gates are applied via teleportation consumption using transverse gates within the modules. The latter approach has the added advantage of being generalizable to any CSS code with transverse CNOT gates, enabling higher coding rates using block codes. Therefore, the proposed method can achieve per second per pair of modules. 10 3A remote logic gate. Considering how to compile advanced algorithms into such modular computers is an interesting problem for future work.

[0079] The photon-based interface between the neutral atom quantum processors of System 100 is capable of operating at 1.12 × 10⁻⁶ ppm. 5 The method generates remote entanglement at a rate of 10 Bell pairs, with fidelity compatible with fault-tolerant computation. It is compatible with existing experimental hardware and can be run with arrays of atoms performing local computations.

[0080] refer to Figure 9 This shows the use of Figure 1 A flowchart of a method 900 for connecting a quantum computing module based on neutral atom qubits in a system 100.

[0081] At operation 902, system 100 initializes an optical tweezer array outside the optical cavity of the first quantum computing module, comprising N > 1 sites, each site having a single atom. The optical cavity consists of multiple mirrors arranged in a twisted ring, which are configured to realize two non-degenerate co-propagation modes with opposite circular polarizations. The energy split between the two non-degenerate co-propagation modes is tuned to match the spacing between the atomic energy levels with opposite spins, so that the atom can simultaneously emit photons of two polarizations into the optical cavity, thereby generating entanglement between the spin state and each polarization.

[0082] At operation 904, system 100 uses a steerable mirror or acousto-optic deflector to position the optical tweezers array 102 ( Figure 3 It is transmitted to the optical cavity.

[0083] At operation 906, system 100 optically pumps the optical tweezers array 102 to... 1 In a single spin state within the ground state S0, F=1 / 2.

[0084] At operation 908, system 100 uses single-qubit rotations applied simultaneously to all qubits to prepare the optical tweezers array as a superposition of spin states. (The last part, "atoms," appears to be incomplete and requires further context.) 171 In the case of Yb, system 100 allows the first atom to use a two-photon optical transition from 1 The ground state S0 F=1 / 2 is excited to 3 D1 F=3 / 2 excited state, in the state of 3 In the superposition of states D1 F=3 / 2 mF=+ / - 3 / 2.

[0085] In all respects, system 100 allows atoms to decay by emitting photons into an optical cavity, which is tuned to interact with the energy emitted from the source. 3 P0 F=1 / 2 mF=+ / - ½ state to 3The D1 F=3 / 2 mF=+ / - 3 / 2 state transition resonance, thus in the atom in 3 An entangled state is generated between the spin and the polarization of the photon in the P0 state;

[0086] At operation 910, system 100 collects photons into the optical fiber and sends the photons to the central router 112. Figure 2 ).

[0087] At operation 912, system 100 infers with photons from the second quantum computing module at the beam splitter, and the coincidence detection of the two photons indicates that an entangled state has been generated between atoms in the first and second quantum computing modules.

[0088] In all respects, system 100 can reinitialize at least two atoms with failed entanglement back to their original state via optical pumping. 1 S0 ground state.

[0089] In various aspects, system 100 can use an acousto-optic deflector or a scannable mirror to move the optical tweezer array out of the optical cavity and into the computing region.

[0090] In various aspects, system 100 can move another array of atomic optical tweezers into the optical cavity.

[0091] In various respects, system 100 can control the crosstalk and reabsorption of photons within the optical cavity by removing atoms that have not undergone entanglement attempts at any point in time from the resonance of the optical cavity.

[0092] In all aspects, system 100 can remove atoms from resonance using the AC Stark displacement of a focused beam array.

[0093] In all aspects, the wavelength of the focused beam array is selected to make 3 P0 to 3 The transition energy of D1 is significantly shifted compared to the coupling between the atom and the optical cavity to prevent photons emitted into the optical cavity from being absorbed by other atoms. The wavelength of the focused beam array can be selected to... 3 The D1 state is used to transfer atoms from 1 S0 is excited to 3 The Rabi frequency of the two-photon transition of P1 shifts significantly.

[0094] In some aspects, system 100 may apply one or more optical displacements to the excited atom while the excited atom is still emitting photons to suppress further photon emission into the optical cavity. In other aspects, one or more optical displacements may be applied after one complete cycle of the oscillation, when there is no excitation in the optical cavity.

[0095] Some embodiments of this disclosure may include some, all, or none of the advantages described above, and / or include one or more other advantages that are readily apparent to those skilled in the art from the accompanying drawings, description, and claims included herein. Furthermore, while specific advantages have been listed above, various embodiments of this disclosure may include all, some, or none of the listed advantages, and / or include other advantages not specifically listed above.

[0096] The embodiments disclosed herein are examples of this disclosure and may be embodied in various forms. For example, although some embodiments herein are described as separate embodiments, each embodiment herein may be combined with one or more other embodiments herein. The specific structural and functional details disclosed herein should not be construed as limiting, but rather serve as the basis for the claims and as a representative basis for teaching those skilled in the art to use this disclosure in different ways with virtually any appropriately detailed structure. Throughout the description of the drawings, the same reference numerals may refer to similar or identical elements.

[0097] The phrases “in embodiments,” “in various embodiments,” “in various embodiments,” “in some embodiments,” or “in other embodiments” may each refer to one or more of the same or different exemplary embodiments provided in this disclosure. The phrase “A or B” means “(A), (B), or (A and B).” The phrase “at least one of A, B, or C” means “(A); (B); (C); (A and B); (A and C); (B and C); or (A, B, and C).”

[0098] It should be understood that the foregoing description is merely illustrative of this disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from this disclosure. Therefore, this disclosure is intended to cover all such alternatives, modifications, and variations. The embodiments described with reference to the accompanying drawings are presented merely to illustrate certain examples of this disclosure. Other elements, steps, methods, and techniques that do not substantially differ from those described in the foregoing and / or appended claims are also intended to fall within the scope of this disclosure.

Claims

1. A device for modular interconnection between quantum processors, comprising: An optical cavity configured to simultaneously collect photons from two transitions having opposite circular polarizations, the optical cavity comprising: Multiple mirrors with a twisted, non-planar annular geometry are configured to achieve two non-degenerate co-propagation modes with opposite circular polarizations.

2. The apparatus of claim 1, wherein the energy splitting between the two non-degenerate co-propagation modes is tuned to match the spacing between atomic energy levels with opposite spins, such that the atoms can simultaneously emit photons of two polarizations into the cavity, thereby generating entanglement between spin states and polarization.

3. The apparatus according to claim 2, wherein the atom is 171 Yb, and wherein the optical cavity is tuned to be from 3 P0 F=1 / 2 mF=+ / - ½ state to 3 D1 F=3 / 2 mF=+ / - 3 / 2 state transition resonance.

4. A system comprising: A device for modular interconnection between quantum processors, the device comprising: An optical cavity configured to simultaneously collect photons from two transitions with opposite circular polarizations, the optical cavity comprising a plurality of mirrors in a twisted, non-planar annular geometry, the plurality of mirrors being configured to realize two non-degenerate co-propagation modes with opposite circular polarizations; and An optical tweezers array configured to be transmitted into the optical cavity using a steerable mirror, the optical tweezers array comprising N > 1 sites.

5. The system of claim 4, further comprising an optical fiber having a first end operatively coupled to the optical cavity, such that the first end of the optical fiber is configured to receive photons emitted by atoms.

6. The system of claim 5, further comprising a central router operatively coupled to a second end of the optical fiber, the central router being configured to receive the photons from the optical fiber.

7. The system of claim 6, wherein the photons from the optical fiber are directed toward a beam splitter in the central router.

8. The system of claim 7, further comprising a second optical fiber from the second module incident on the beam splitter, wherein the central router is reconfigured to direct photons from different module pairs toward each beam splitter in the beam splitter array.

9. A method for connecting a quantum computing module based on neutral atom qubits, the method comprising: An optical tweezers array comprising N > 1 sites, each site containing a single atom, is initialized outside the optical cavity of the first quantum computing module. The optical cavity consists of multiple mirrors arranged in a twisted ring, configured to realize two non-degenerate co-propagation modes with opposite circular polarizations. One of the multiple mirrors is configured as an output coupler, and the energy split between the two non-degenerate co-propagation modes is tuned to match the spacing between the atomic energy levels with opposite spins, such that the atom simultaneously emits photons of both polarizations into the optical cavity, thereby generating entanglement between the spin state and each polarization. The optical tweezers array is transferred into the optical cavity using a steerable mirror or an acousto-optic deflector; Optically pump the optical tweezers array to 1 In a single spin state within the ground state S0, F=1 / 2; and The optical tweezers array is prepared as a superposition of spin states by simultaneously performing single-qubit rotations on all qubits.

10. The method according to claim 9, wherein the atom is 171 Yb, and the method further includes: Allowing the first atom to use two-photon optical transitions from 1 The ground state S0 F=1 / 2 is excited to 3 D1 F=3 / 2 excited state, in the state of 3 In the superposition of states D1 F=3 / 2 mF=+ / - 3 / 2.

11. The method of claim 10, further comprising: The atoms are allowed to decay by emitting photons into the optical cavity, which is tuned to interact with the atoms emitted from the optical cavity. 3 P0 F=1 / 2 mF=+ / - ½ state to 3 The D1 F=3 / 2 mF=+ / - 3 / 2 state transition resonance, in the state of 3 An entangled state is generated between the spin of the atom in the P0 state and the polarization of the photon; The photons are collected into an optical fiber and the image is sent to a central router. as well as Interference with photons from the second quantum computing module occurs at the beam splitter, and the coincidence detection of the two photons indicates the generation of an entangled state between atoms in the first and second quantum computing modules.

12. The method of claim 11, further comprising reinitializing at least two atoms with failed entanglement back to the original state via optical pumping. 1 S0 ground state.

13. The method of claim 9, further comprising: The optical tweezers array is moved out of the optical cavity and into the computing region using an acousto-optic deflector or a scannable mirror; as well as Another array of atomic optical tweezers is moved into the optical cavity.

14. The method of claim 11, wherein information about the arrival time of the detected photon is used to infer the error probability on the resulting Bell pair, and the information is used in the computation of the quantum error correction code to perform an estimation of the logical quantum bit state.

15. The method of claim 9, further comprising controlling crosstalk and reabsorption of photons within the optical cavity by removing atoms in the optical cavity that have not undergone entanglement attempts at any point in time from the resonance of the optical cavity.

16. The method of claim 15, wherein the atoms are removed from the resonance using the AC Stark displacement of the focused beam array.

17. The method of claim 16, wherein the wavelength of the focused beam array is selected such that... 3 P0 to 3 The transition energy of D1 is significantly shifted compared to the coupling between the atom and the optical cavity, to prevent photons emitted into the optical cavity from being absorbed by other atoms.

18. The method of claim 16, wherein the wavelength of the focused beam array is selected such that... 3 The D1 state is used to transfer atoms from 1 S0 is excited to 3 The Rabi frequency of the two-photon transition of P1 shifts significantly to control the state of... 1 Which atom in the S0 state is excited to the state described? 3 In the D1 state, an attempt is made to initiate spin-photon entanglement.

19. The method of claim 9, further comprising: While the excited atoms are still emitting photons, one or more optical shifts are applied to the excited atoms to suppress further photon emission into the optical cavity.

20. The method of claim 19, wherein the application of the one or more optical shifts occurs when the atom has completely decayed to... 3 This occurs before the P0 state, at a time when there is no photon excitation in the optical cavity.

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