Quantum networking nodes and protocols with multiple qubit species

Abstract

The present disclosure describes various aspects of using multiple species in a trapped ion node for quantum networking. In one aspect, a quantum networking node is described that includes: a plurality of storage qubits, each storage qubit based on 171 Yb + atomic ions; and one or more communication qubits, each communication qubit based on 138 Ba + Atomic ions. The storage and communication qubits are part of a lattice in an atomic ion trap. In another aspect, a quantum computing system having a modular optical architecture is described, comprising: a plurality of quantum networking nodes, each of which comprises a plurality of storage qubits (e.g., based on 171 Yb + atoms and ions) and one or more communicating qubits (e.g., based on 138 Ba + The system further comprises a photon entangler coupled to each of the plurality of quantum networking nodes.

Description

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This patent application claims priority to U.S. Non-Provisional Application No. 16 / 182,219, filed on November 6, 2018, entitled “QUANTUM NETWORK NODE AND PROTOCOLS WITH MULTIPLE QUBIT SPECIES,” and U.S. Provisional Patent Application No. 62 / 582,529, filed on November 7, 2017, entitled “QUANTUM NETWORK NODE AND PROTOCOLS WITH MULTIPLE QUBIT SPECIES,” and also claims priority to and the benefit of U.S. Provisional Patent Application No. 62 / 694,604, filed on July 6, 2018, entitled “QUANTUM NETWORK NODE AND PROTOCOLS WITH MULTIPLE QUBIT SPECIES,” the contents of which are incorporated herein by reference in their entirety. Background Art

[0003] Aspects of the present disclosure relate generally to quantum information processing, and more particularly, to techniques for utilizing multiple species in trapped ion nodes for quantum networking.

[0004] Trapped atomic ions are one of the quantum information processing (QIP) approaches that have provided general and fully programmable machines. Trapped atomic ions are also the main platform for quantum information networks (QINs). There is a need for systems or networks based on trapped atomic ions that can improve the overall communication of such systems or networks. Summary of the invention

[0005] A brief summary of one or more aspects is given below to provide a basic understanding of these aspects. This summary is not an exhaustive review of all aspects considered, and is neither intended to identify the key or important elements of all aspects, nor to delineate the scope of any or all aspects. Its purpose is to present some concepts of one or more aspects in a brief form as a prelude to a more detailed description presented later.

[0006] Trapped atomic ions are the main platform for QINs, with long-lived identical qubit memories that can be entangled locally through their Coulomb interactions and remotely through photonic channels. In order to perform local and remote operations in a single node of a quantum network, extreme isolation is required between the spectator qubit memory and the qubits associated with the photonic interface. This disclosure describes how to achieve this goal by co-trapping qubits in the same node. 171 Yb+ and 138 Ba + The present disclosure also describes requirements for scalable ion trap networking nodes based on the results of two different experiments, including entanglement of mixed-species qubit pairs through their collective motion and entanglement of mixed-species qubit pairs through their collective motion. 138 Ba + The qubit is entangled with the emitted visible photon.

[0007] In one aspect of the present disclosure, a quantum networking node for use in a modular optical architecture for quantum computing is described, the quantum networking node comprising: a plurality of storage qubits, each storage qubit being based on 171 Yb + atomic ions; and one or more communication qubits, each communication qubit being based on 138 Ba + Atomic ions. The plurality of storage qubits and the one or more communication qubits may be part of a lattice in an atomic ion trap.

[0008] In another aspect of the present disclosure, a quantum computing system with a modular optical architecture is described, the quantum computing system comprising a plurality of quantum networking nodes and a photon entangler coupled to each of the plurality of quantum networking nodes. Each quantum networking node comprises: a plurality of storage qubits, each storage qubit is based on 171 Yb + atomic ions; and one or more communication qubits, each communication qubit being based on 138 Ba + Atomic ions. The plurality of storage qubits and the one or more communication qubits may be part of a lattice in an atomic ion trap. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] The drawings depict only some embodiments and therefore should not be considered limiting in scope.

[0010] Figure 1 is a diagram illustrating an example of a multi-species ion trap network according to aspects of the present disclosure.

[0011] FIG. 2( a) and FIG. 2( b) are diagrams showing a plurality of bases according to various aspects of the present disclosure. 138 Ba + Illustration of an example of the correlation between a qubit and the emitted photon polarization.

[0012] Figure 3 is a diagram showing the non-resonant coupling of 532 and 355 nm pulsed laser beams into a 138 Ba + and 171Yb + Of the two 2 P 1 / 2 and 2 P 3 / 2 Illustration of examples of energy levels.

[0013] Figure 4(a) and 4(b) FIG. 1 is a diagram showing a common capture for lateral and axial motion according to aspects of the present disclosure. 138 Ba +_171 Yb + Illustration of an example of a vibrational spectrum of a crystal.

[0014] Figure 5(a) and 5(b) is to show that the direct use of collective motion according to various aspects of the present disclosure will 138 Ba + The state is mapped to 171 Yb + A graphic representation of an example of the experimental steps and results.

[0015] Figure 6(a) and 6(b) is a diagram showing the π / 2 rotation after the entangled MS gate and MS interaction according to various aspects of the present disclosure. 171 Yb + and 138 Ba + Illustration of an example of the measurement probability of a qubit state.

[0016] Figure 7(a)-7(c) is a diagram showing examples of networking nodes, photon entanglers, and wavelength converters according to aspects of the present disclosure.

[0017] Figure 8 is a block diagram illustrating an example of a trapped ion based QIP system according to aspects of the present disclosure.

[0018] Fig. 9 is a diagram illustrating an example of a computer device according to aspects of the present disclosure. DETAILED DESCRIPTION

[0019] The detailed description set forth below in conjunction with the accompanying drawings is intended as a description of various configurations and is not intended to represent the only configuration in which the concepts described herein may be practiced. This detailed description includes specific details to provide a thorough understanding of the various concepts. However, it will be apparent to those skilled in the art that these concepts may be practiced without these specific details. In some cases, well-known components are shown in block diagram form to avoid obscuring these concepts.

[0020] Trapped atomic ions are one of the most advanced platforms for quantum information networks (QINs), hosting qubit memories that are inherently identical and have unparalleled coherence. A single node of the network can be implemented with a string of trapped ions, where local entanglement gate operations use external control fields that couple the qubit states through their collective motion. The edges of the network can then be realized by photonic entanglement operations between selected "communication" qubits in separate nodes. However, the photonic interface for the communication qubit may not interfere with the observation of the storage qubit, as even a single resonant photon will destroy the quantum memory. This isolation is best achieved by using two different atomic ions: one for local processing and storage, and the other for communication with other nodes, such as Figure 1 as shown in .

[0021] Figure 1 A diagram 100 is shown having a network of ion traps of various types, wherein 138 Ba + The communication qubit 125 is coupled to the optical fiber. Using photons entangled with their parent atoms, for example, any pair of different nodes 110a, 110b and 110c can be entangled by the reconfigurable photon entangler 120 138 Ba + The local Coulomb interaction mediates the transfer of entanglement to nearby 171 Yb + Storage qubits 115 and quantum logic gates within nodes. Two types (e.g., 171 Yb + Storage qubits 115 and 138 Ba + The dissimilar or different electronic transition frequencies of the communicating qubits 125 provide the necessary isolation to protect 171 Yb + Storage qubit 115 is protected from 138 Ba + Influence of resonance processes in photonic interfaces.

[0022] This disclosure describes different components or requirements for multiple types of ion trap nodes for potential quantum networks. These requirements can include coherent quantum state mapping between storage qubits and communication qubits, and the generation of photon qubits entangled with communication qubits. For example, storage qubits can be 171 Yb + Atomic Ions 2 S 1 / 2 The ground state hyperfine "clock" energy level is encoded, and For communicating qubits, the present disclosure proposes using 138 Ba + Atomic Ions2 S 1 / 2 Ground state electron spin energy level, |J=1 / 2,m J =-1 / 2>≡|↓> and |J=1 / 2,m J =+1 / 2>≡|↑>. 138 Ba + The system features relatively long wavelength photon emission lines (e.g., 493 nanometers (nm) and 650 nm), which eases the technical requirements for photonic interfaces and provides comparable performance to 369 nm. 171 Yb + The present disclosure describes the necessary isolation of the resonance. 171 Yb + The coherence time of the qubit (~1.5 s) is not affected by fluorescence or continuous Doppler freezing with the qubit being located only a few microns away. 138 Ba + The isolation between the two species is verified by the effect of the driving laser associated with the qubit. 138 Ba + ions are used in a similar setup for sympathetic freezing, applying a dynamic decoupling pulse, 171 Yb + The coherence time of the ultrafine qubit exceeds 10 minutes.

[0023] Standard spin-dependent fluorescence collection can be used 171 Yb + Near-perfect single-shot detection of a qubit state. 138 Ba + Ion qubits lack such isolated cyclic transitions, so to detect 138 Ba + The lack of isolated loop transitions is not a problem in multi-class network architectures because 138 Ba + The qubit is used only as 171 Yb + The link between the storage qubits. Once through the Coulomb-based gate 138 Ba + The qubits are mapped to adjacent 171 Yb + memory, quantum information processing does not have to rely on 138 Ba + However, implementing state measurement techniques is difficult 138 Ba + Calibration and diagnostics of the system are still useful.

[0024] In addition to being used as photonic communication qubits,138 Ba + Ions are used 171 Yb + Interactive freezing of qubits to maintain occupied low-motion phonon eigenstates for higher-fidelity quantum operations. Electromagnetically induced transparency (EIT) freezing can be achieved using a 493nm laser beam tuned to 2 S 1 / 2 – 2 P 1 / 2 This laser beam induces a narrow atomic laser shaping state resonance in which the red sideband transition is selectively excited, while the blue sideband and carrier transitions are suppressed. Using this technique, 138 Ba + and 171 Yb + The motion of the two-ion crystal is frozen to (out-of-phase mode) and (In-phase mode).

[0025] Communication qubits may not require long coherence times, since information can be quickly transferred to storage qubits, where it can be stored and used later. However, the high magnetic field sensitivity of about 2.8kHz / mG caused by Zeeman 138 Ba + The short coherence time of qubits can cause errors during information transfer operations. An arbitrary waveform generator can be used to apply a magnetic field at 60 Hz and higher harmonics with full phase and amplitude control to partially cancel the background magnetic field. This technique can 138 Ba + The coherence time increases from 100 microseconds (μs) to about 4 milliseconds (ms), which is much longer than any transmission operation gate time.

[0026] Through the post-selection process 138 Ba + The qubit is entangled with the emitted photon, demonstrating the photonic interface. For example, within about 1 μs, the qubit can be initialized to the |↓> state and emitted with probability P exc ≈10% weakly excites it to 2 P 1 / 2 ||J=1 / 2,m J = +1 / 2> energy level. To achieve an average experimental repetition rate of ~500kHz, a 50μs Doppler freezing light can be applied after 50 entanglement attempts. After excitation, the atom decays back to the |↓> state, emitting σ + polarized photons, or decay to the |↑> state, emitting π-polarized photons. Photons perpendicular to the quantization axis are collected; therefore, on this basis, π photons are recorded as vertically polarized (|V>), while σ+ The photon is recorded as horizontally polarized (|H>). Assuming that one photon is collected, this would ideally result in 138 Ba + Entangled state between qubit and photon polarization qubit |↓>|V>+|↑>|H>.

[0027] Figure 2(a) and Figure 2(b) show the 138 Ba + More specifically, Figures 2(a) and 2(b) show correlation measurements between the states of atomic and photon qubits in multiple bases, and from these measurements the (post-selected) entanglement fidelity can be inferred as The error may be attributed to polarization mixing (10%) caused by the large solid angle, multiphoton scattering during the excitation step (e.g., P exc / 4 = 2.5%) and imperfect state initialization or detection (e.g., 1%). These error sources can be greatly reduced by collecting photons along the quantization axis and rapidly exciting the atoms using pulsed lasers.

[0028] Referring again to FIG. 2( a ), a diagram 200 shows the detection of the photon qubit state |V> (light blue) or |H> (dark red) under the condition that the photon qubit state |V> (light blue) or |H> (dark red) is detected using a photomultiplier tube (PMT). 138 Ba + The measurement probability that the qubit is at |↑>. A half-wave plate (HWP) rotates the photonic qubit and the data shows two measurements corresponding to HWP angles of 0 and π / 4.

[0029] Referring again to FIG. 2( b ), diagram 250 shows that by fixing the HWP at π / 8, the photon polarization is rotated such that |H>→|H>-|V> and |V>→|H>+|V>. Subsequent photon detection projects the atom into the superposition (|↑>+|↓>)|H>+(|↑>-|↓>)|V>. Then, upon detection of a |V> or |H> photon, the atomic superposition state coherently rotates by a π / 2 rotation to |↓> and |↑>, with a phase of π / 2 or 3π / 2, restoring the high correlation between the qubit and the photon.

[0030] In addition to the above aspects, this disclosure also describes a deterministic quantum gate between two species in a quantum networking node. 171 Yb + and 138 Ba +Coherent information exchange is performed between qubits while driving coherent Raman transitions in both atomic ions (e.g., in both atomic ions). The direct Cirac-Zoller (CZ) mapping process by resonant coupling to the collective motion of the trapped ions and the dispersive (dispersive) between qubits are further described below. (MS) Quantum gate.

[0031] Non-copropagating Raman beams (e.g., beams propagating in different directions) can be introduced using Nd:YVO4 mode-locked pulsed lasers (Spectra-Physics Vanguard), which can drive transitions between different vibrational eigenmodes and qubit states. Figure 3 As shown in diagram 300 in FIG. , these beams couple non-resonantly to the excited levels, where for 171 Yb + system, using triple frequency 355nm output, and for 138 Ba + The system uses twice the frequency of the 532nm output from the same laser. When the beat-note frequency between the two beams is close to the qubit splitting, the stimulated Raman transition is driven. The linear polarizations can be chosen to be all perpendicular to the quantization axis, allowing the desired Raman transition to be driven while minimizing the differential ac Stark shift on each species. The large bandwidth of the frequency comb easily spans the Raman rotation 171 Yb + The qubit frequency is 12.642821 GHz. To stabilize the beat tone frequency of the two Raman beams, a feed-forward technique can be used to modulate one of the 355 nm beams to compensate for any changes in the laser repetition rate. 138 Ba + The qubit splitting is only a few megahertz, so multiple comb tooth spacings may not be needed to drive transitions on this qubit, and thus metronomic stabilization may not be needed on the 532nm beam.

[0032] Refer to Figure 3 , Figure 3 Shown in 138 Ba + and 171 Yb + 532 and 355 nm pulsed laser beams in atomic systems 2 P 1 / 2 and 2 P 3 / 2 Anharmonic coupling of energy levels to drive stimulated Raman transitions, with polarizations indicated. Figure 3 The splits shown in FIG. 5 are for illustration purposes and are not necessarily shown to scale.

[0033] Although the 355 nm radiation is nominally coupled only to171 Yb + qubit and 532nm radiation is coupled to 138 Ba + qubit, but with a small amount of crosstalk coupling to another atomic system. For the same intensity and without considering the comb spectrum or light polarization, 171 Yb + The system can sense an effective Rabi frequency from 532nm radiation that is ~2.6% of the nominal 355nm radiation Rabi frequency. 138 Ba + The system can sense ~11% Rabi frequency from 355nm radiation. However, the laser polarization and frequency comb spectra required for the two atomic qubit transitions are different, and these aspects can be used to reduce the crosstalk between the two systems to much less than 1%. For both atomic species, the spontaneous Raman scattering rate for each qubit Rabi cycle may be less than 10 -5 , resulting in a single (two) qubit gate with an error of less than 10 -5 (10 -4 ).exist 138 Ba + The rare spontaneous scattering from 532 nm in the system appears to 138 Ba + System Pass 2 P 3 / 2 The energy level is optically pumped to a metastable 2 D 5 / 2 state, which has a lifetime of 32 seconds. These rare pumping events can be overcome by, for example, illuminating the ions with a diffuse 1 Watt orange light-emitting diode (centered at 617 nm) that excites the ions at 614 nm with sufficient intensity. 2 D 5 / 2 to 2 P 3 / 2 transition to return the ion to the ground state in about 30 milliseconds.

[0034] Although they have similar atomic masses, for a given mode a coupled pair 138 Ba + and 171 Yb + The transverse motion of the ions exhibits a large mismatch in amplitude, resulting in less kinematic coupling between the ions, as shown in diagram 400 in FIG. 4( a ), described in more detail below. Therefore, a better matched axial mode may be used instead, as shown in diagram 450 in FIG. 4( b ), described in more detail below. As the number of ions in the crystal chain increases, the kinematic eigenvector mismatch in the transverse modes becomes less pronounced, and these modes may be conveniently used to benefit from higher mode frequencies.

[0035] Figures 4(a) and 4(b) show the co-capture of the lateral (Figure 4(a)) and axial (Figure 4(b)) motions. 138 Ba + – 171 Yb + Raman sideband vibration spectrum of the crystal as a function of detuning from the carrier transition, where the shared motion phonon state is preserved, with the probability of measuring a change in the qubit state plotted in light blue. 138 Ba + , dark purple indicates 171 Yb + Peaks at positive (negative) values ​​correspond to blue (red) sideband transitions, where a spin flip is accompanied by the addition (subtraction) of a phonon. The sidebands corresponding to in-phase (IP) and out-of-phase (OP) are labeled for the transverse (x, y) and axial (z) directions of motion, with their theoretical eigenvector magnitudes shown on the right. Unlabeled peaks correspond to higher-order sidebands, and interactions involving multiple modes, such as subtraction of phonons from one mode and addition of phonons to another.

[0036] First, by directly using the collective motion in the Cirac-Zoller (CZ) mapping scheme 138 Ba + The quantum bit state is converted to 171 Yb + The process is shown in diagram 500 of FIG. 5( a ) and described in more detail below, starting with EIT freezing and preparing through carrier transitions. 138 Ba + The spin state begins. Next, 138 Ba + The red sideband π rotation on the system transfers information to the shared phonon mode, which is then transferred to 171 Yb + Quantum bits, at the same time 171 Yb + A further red sideband π rotation is performed on the system. As shown in the diagram 550 of FIG. 5( b ), and as will be described in more detail below, the total state transfer efficiency of 0.75 is mainly limited by the purity of the initial motion state. However, the main disadvantage of the CZ method is that the communication qubit and the CZ mapping operation must be phase coherent. Because the communication qubit may be entangled preferentially through the photon channel, the CZ mapping method requires that the beam path be stabilized to much better than the wavelength of light.

[0037] Referring again to FIG. 5( a ), a diagram 500 shows the above-mentioned direct use of collective motion to 138 Ba + The state is mapped to171 Yb + As described above, the process begins with EIT freezing (530), followed by initializing the qubit state (QI) to |↓> and (505, 535). After initialization, within time T 138 Ba + The stimulated Raman rotation R(T) (510) of the qubit prepares the state to be transmitted. 138 Ba + A red sideband π rotation (RSBπ) (515) on the qubit transfers this information to a shared phonon mode, which is then transferred to the qubit via another RSB π rotation (520). 171 Yb + In the final step, we can measure 171 Yb + Qubit state (525).

[0038] Referring again to FIG. 5( b ), a diagram 550 shows a representative 138 Ba + Discovery of the function of qubit rotation time T 171 Yb + The quantum bit is The observed state transfer efficiency is ≈0.75.

[0039] In addition to the above features, a method is described that alleviates the above limitations. (MS) transmission method. In the MS transmission scheme, the entanglement and state transfer fidelity only need to be constrained within the Lamb-Dicke limit, which can be achieved by 300μs Doppler freezing followed by 500μs EIT freezing. The MS entanglement gate can be implemented in the system described in this paper by using pairs of non-copropagating Raman beams to simultaneously address the axial out-of-phase modes with symmetric detuning δ. Since the 355 and 532nm pulse pairs follow different paths, they are not necessarily incident on the atoms at the same time. Importantly, the temporal overlap between these pairs is not required for MS interactions. Spin-dependent forces using Raman beams can be applied to each atom at different times. The result is only a static phase on the entangled state, which can be controlled by adjusting the optical path length or the difference between the radio frequency (RF or rf) beat note phases of the 355nm and 532nm drive fields. These spin-dependent forces displace the motion wave packets of a certain two qubit states in phase space. Walsh modulation can be included to suppress frequency and timing errors, and after a gate time T = 200 μs (detuning δ = 10 kHz), the motion returns to its original state, acquiring the geometric phase as in a usual MS gate. The light intensity of the drive field is adjusted to obtain a carrier Rabi frequency of Ω = δ / 4η, resulting in a π / 2 geometric phase after the MS interaction, where η is the Lamb-Dicke parameter. We find the correct optical force phase by monitoring the acquired geometric phase. To maintain the relative optical force phase from shot to shot, the same arbitrary waveform generator can be used to drive the AOMs of the 355 and 532 nm laser beams. The fidelity of this operation is approximately like Figure 6(a) and 6(b) and this low fidelity can be attributed to, for example, excessive heating of the axial out-of-phase mode

[0040] FIG. 6( a ) shows a diagram 600 showing the effect of applying an entangled MS gate to an initial After the state, 171 Yb + and 138 Ba + The probability of measuring the state of a qubit. Ideally, this interaction will produce maximum entanglement The optical phase of the driving field is imprinted on the gate phase φ S on the spin.

[0041] FIG6( b ) shows a diagram 650 after the MS interaction, where a π / 2 rotation is applied to both qubits. 171 Yb + When the π / 2 rotation phase is scanned, 138 Ba+ The phase of the π / 2 pulse is kept constant. The data is shown at the point of maximum parity. Measured qubit state probabilities.

[0042] Even if the phase of the light field is imprinted on the entangled state after this interaction, two consecutive MS gates with a relative π phase difference can be used to transfer information from a communicating qubit (e.g. 138 Ba + qubit) is coherently transferred to a storage qubit (e.g. 171 Yb + Therefore, the phase coherence between remote and local entanglement operations in quantum networks can be established without directly eliminating the optical phase dependence from the MS gates through additional single-qubit operations or special beam geometries.

[0043] Based on the various techniques and aspects described in the present disclosure, photonic Bell state analyzers can be used to make photonic connections to expand quantum networks to many nodes. In order to expand to many interconnected nodes, the atom-photon and atom-atom entanglement fidelity and rate can be greatly improved. First, it is expected that photonic qubits will be encoded as two different frequencies instead of polarization, which will significantly improve the fidelity of long-distance communication qubits. Secondly, it is expected to use fabricated chip traps with integrated optical elements to increase the connection rate between nodes. In addition, the positional stability of ions derived from the uniformity and repeatability of the structure and the high light access microfabricated ion traps compared to hand-assembled traps (for example, Sandia National Laboratory's high light access microfabricated ion traps, )Comparable heating rates could potentially allow higher-fidelity kinematic gates between memory and communication qubits in these fabricated traps.

[0044] Other aspects related to the various types of ion trap networks described above are described below. For example, quantum networking nodes (e.g., Figure 1 The nodes 110a, 110b, and 110c in FIG. 1 may include: a plurality of storage qubits (e.g., storage qubit 115), each storage qubit based on 171 Yb + atomic ions; and one or more communication qubits (e.g., communication qubit 125), each communication qubit based on 138 Ba + The plurality of storage qubits and the one or more communication qubits may be part of a lattice in an atomic ion trap (see, for example, Figure 8 In one example, the lattice can be a linear lattice.

[0045] In one aspect of such a quantum networking node, the storage qubit of one of the storage qubits 171 Yb + The atomic ion and one of the communicating qubits 138 Ba + The local connection between the atomic ions is established by at least partially controlling the collective motion of the one storage qubit and the one communication qubit by an external laser field to couple the one storage qubit and the one communication qubit, the external laser field being configured to direct the collective motion of the one storage qubit to the one communication qubit. 171 Yb + Atomic ions and / or said one communicating qubit 138 Ba + For example, the atomic ion trap can be configured to receive a single laser whose second harmonic corresponds to the one communication qubit. 138 Ba + A first external laser field exerts a force on the atomic ion, and the third harmonic of the single laser corresponds to the first external laser field exerting ... first storage qubit. 171 Yb + A second external laser field exerts a force on the atoms and ions. In addition, the second harmonic of the single laser is at an emission line at a wavelength of about 532 nm, and wherein the third harmonic of the single laser is at an emission line at a wavelength of about 355 nm.

[0046] In another aspect of this quantum networking node, the 171 Yb + Atomic ions are the first atomic species, the 138 Ba + The atomic ion is a second atomic species, and the atomic mass of the first atomic species and the atomic mass of the second atomic species are substantially similar, with the atomic mass difference between the two atomic masses being less than 25%.

[0047] In another aspect of such a quantum networking node, the one or more communication qubits include a plurality of communication qubits, and the quantum networking node is configured to multiplex between the plurality of communication qubits to enable repeated trials of photon emission from the plurality of communication qubits. In addition, the one or more communication qubits include a plurality of communication qubits located at one end of the lattice, at the other end of the lattice, or at both ends of the lattice. For example, FIG. 7( a) shows diagrams 700, 710, and 720, which show examples of a node 110 having a plurality of communication qubits 125. Diagram 700 shows a node 110 having a plurality of communication qubits (e.g., communication bits 125), wherein at least one communication qubit is located at each end of the lattice (also including storage qubits 115). Diagram 710 shows a node 110 having a plurality of communication qubits (e.g., communication qubits 125) at one end of the lattice (which also includes storage qubits 115). Diagram 720 shows node 110 having a plurality of communication qubits (e.g., communication qubit 125) at the other end of the lattice (also including storage qubit 115).

[0048] In another aspect of such a quantum networking node, the 138 Ba + The atomic ions are configured to emit photons by fluorescence, and the emitted photons are 138 Ba + Atomic ion entanglement. In one example, at least a portion of the spectrum of the emitted photons is in the visible spectrum. The emission line of the emitted photons can be coupled to the plurality of storage qubits. 171 Yb + Resonant isolation of atomic ions. The emission lines may include emission lines at wavelengths of approximately 493 nm and 650 nm, and wherein 171 Yb + The resonance of the atomic ion is at a wavelength of about 369 nm. The emission lines at wavelengths of about 493 nm and 650 nm may correspond to the 138 Ba + The electronic ground-level Zeeman qubit state of the atomic ion is connected to the excited state of visible light.

[0049] In another aspect of such a quantum networking node, each storage qubit can be configured to have a corresponding 171 Yb + Atomic Ions 2 S 1 / 2 The ground state hyperfine level is encoded. The corresponding 171 Yb + The coherence time of the hyperfine state of atomic ions is about 1.5 seconds or longer.171 Yb + The splitting of the hyperfine qubit states of atomic ions is highly insensitive to magnetic field fluctuations (much smaller than the 1.4 MHz / Gauss of the electron magnetic moment or "Bohr magneton"). In addition, each storage qubit can be further configured for initialization and detection without having to shuttle the atomic state population between hyperfine energy levels.

[0050] In another aspect of such a quantum networking node, each communicating qubit can be configured to use 138 Ba + Atomic Ions 2 S 1 / 2 Ground state electron spin energy level.

[0051] Another example related to the above-mentioned multi-type ion trap network can be a quantum computing system with a modular optical architecture, which can include multiple quantum networking nodes (e.g., Figure 1 110a, 110b, and 110c), wherein each quantum networking node includes: a plurality of storage qubits (e.g., storage qubit 115), each storage qubit based on 171 Yb + atomic ions; and one or more communication qubits (e.g., communication qubit 125), each communication qubit being based on 138 Ba + Atomic ions. The plurality of storage qubits and the one or more communication qubits may be atomic ion traps (see, for example, Figure 8 The system may further include a photon entangler coupled to each of the plurality of quantum networking nodes (e.g., Figure 1 Photon entanglement device 120 in it).

[0052] In one aspect of such a quantum computing system, each storage qubit in each of the plurality of quantum networking nodes is configured to store qubits in the corresponding 171 Yb + Atomic Ions 2 S 1 / 2 The ground state hyperfine level is encoded.

[0053] In another aspect of this quantum computing system, each communication qubit in each of the plurality of quantum networking nodes is configured to use the 138 Ba + Atomic Ions2 S 1 / 2 Ground state electron spin energy level.

[0054] In another aspect of such a quantum computing system, a first communication qubit of the one or more communication qubits of a first quantum networking node of the plurality of quantum networking nodes is entangled with one of the one or more communication qubits of a second quantum networking node of the plurality of quantum networking nodes. In addition, a second communication qubit of the one or more communication qubits of the first quantum networking node is entangled with one of the one or more communication qubits of a third quantum networking node of the plurality of quantum networking nodes.

[0055] In another aspect of this quantum computing system, any one of the one or more communication qubits in one of the plurality of quantum networking nodes 138 Ba + The atomic ions are configured to emit photons by fluorescence, and the emitted photons are 138 Ba + Atomic ion entanglement. At least a portion of the spectrum of the emitted photons is in the visible spectrum. In addition, the photon entangler is coupled to each of the multiple quantum networking nodes via an optical fiber configured to operate on an optical communication spectrum, and the quantum computing system also includes a wavelength converter to convert the visible spectrum of the emitted photons into an optical communication spectrum. In one example, the optical communication spectrum includes a wavelength of approximately 1300-1550nm. The photon entangler may include one or more optical components compatible with the optical communication spectrum. For example, the photon entangler may include one or more reconfigurable optical switches to enable entanglement between any two quantum networking nodes from the multiple quantum networking nodes. Figure 7(b) and 7(c) Examples of photon entanglers and wavelength converters are shown respectively. For example, the diagram 730 in FIG. 7( b) shows a photon entangler 120 having one or more optical components 735 a, ..., 735 n, where these components may include components compatible with the optical communication spectrum as described above, such as a reconfigurable optical switch. The diagram 750 in FIG. 7( c) shows a wavelength converter 760, which is configured to convert light and / or photons carrying some form of information from the visible spectrum to the optical communication spectrum.

[0056] Although the above 171 Yb + Storage qubits 115 and 138 Ba +Communication qubit 125 Various examples of storage qubit 115 and communication qubit 125 are described, but it should be understood that these examples are provided for purposes of illustration and not limitation. Storage qubit 115 and communication qubit 125 may be selected to be sufficiently different so that communication qubit 125 does not affect the function of storage qubit 115. This may be achieved by making storage qubit 115 and communication qubit 125 (1) composed of different ion species, (2) composed of different isotopes of the same species, as long as there is sufficient difference, (3) selecting different qubit basis states (e.g., hyperfine states versus other types of states), or (4) a combination of the above.

[0057] For example, regarding different ion species, Yb / Ba can be used as described above, but Ca / Sr, Be / Mg or any combination of these can also be used. Others may also include Cd, Zn, Al, etc. For these species, different isotopes can be used. For example, for Yb / Ba, any one of 171Yb, 174Yb, 176Yb or 172Yb, etc. and any one of 138Ba, 137Ba, 133Ba, etc. can be used. For Ca / Sr, any one of 40Ca, 43Ca, etc. and any one of 88Sr, 87Sr, 86Sr, etc. can be used. For Be / Mg, 9Be and any one of 24Mg, 25Mg, 26Mg, etc. can be used.

[0058] When using the different ion species described above, the choice of each qubit can be hyperfine (odd isotopes of each ion species), Zeeman (any of these species), or optical qubit (e.g., for Yb, Ba, Ca, Sr, and Mg).

[0059] Also as described above, different isotopes of the same kind may be used for storage qubit 115 and communication qubit 125. For example, two of 171Yb, 174Yb, 176Yb, or 172Yb, etc. may be used for storage qubit and communication qubit, two of 138Ba, 137Ba, 133Ba, etc. may be used for storage qubit and communication qubit, two of 40Ca, 43Ca, etc. may be used for storage qubit and communication qubit, two of 88Sr, 87Sr, 86Sr, etc. may be used for storage qubit and communication qubit, or two of 24Mg, 25Mg, 26Mg, etc. may be used for storage qubit and communication qubit.

[0060] Furthermore, different nodes 110 may be made using different combinations of storage qubits 115 and communication qubits 125. For example, one node 110 may be made using one set of ion species (e.g., Yb / Ba), and another node 110 may be made using another set of ion species (e.g., Ca / Sr or Be / Mg). In another example, one node 110 may be made using one set of isotopes of the same species (e.g., different isotopes of Yb), while another node 110 may be made using another set of isotopes of the same species (e.g., different isotopes of Ca). Nodes made from different combinations of different sets of ion species, different sets of isotopes of the same species, and / or different qubit selections of qubit basis states (e.g., hyperfine) may be used as part of a multi-species ion trap network, as described above. Figure 1 As described in FIG. 100 .

[0061] Figure 8 800 according to various aspects of the present disclosure. The QIP system 800 may also be referred to as a quantum computing system, a quantum computing network, a computer device, etc. In one aspect, the QIP system 800 may correspond to Figure 1 Parts of a network of multiple ion traps or Fig. 9 A quantum computer implementation of computing device 900 in FIG.

[0062] The QIP system 800 may include a source 860 that provides atomic species to a chamber 850 having an ion trap 870 that captures the atomic species ionized by the optical controller 820. The light source 830 in the optical controller 820 may include one or more laser sources that may be used for ionization of the atomic species, control of the atomic ions (e.g., phase control), fluorescence of the atomic ions that may be monitored and tracked by an image processing algorithm running in an imaging system 1040 in the optical controller 1020, and / or for other aspects, including those described above in connection with quantum networking using multiple species in trapped ion nodes. The imaging system 840 may include a high-resolution imager (e.g., a CCD camera) for monitoring the atomic ions as they are provided to the ion trap 870 (e.g., for counting) or after they are provided to the ion trap 870 (e.g., for monitoring the atomic ion state). In one aspect, the imaging system 840 may be implemented separately from the optical controller 820, however, the use of fluorescence to detect, identify, and label the atomic ions using an image processing algorithm may require coordination with the optical controller 820.

[0063] The QIP system 800 may also include an algorithm component 810 that may operate with other parts of the QIP system 800 (not shown) to perform quantum algorithms (e.g., QFT, quantum simulation) utilizing the above-described embodiments. The algorithm component 810 may provide instructions to various components of the QIP system 800 (e.g., to the optical controller 1020) to enable implementation of quantum circuits or their equivalents. That is, the algorithm component 810 may allow different computational primitives to be mapped into physical representations using, for example, the ion trap 870.

[0064] QIP System 800 can achieve Figure 1 One or more components or structures shown in the various types of ion trap networks in diagram 100, and Figure 7(a) , 7(b) and some or all of the components shown in 7(c).

[0065] Reference now Fig. 9 , an example computer device 900 according to aspects of the present disclosure is shown. For example, computer device 900 may represent at least a portion of a single computing device, a plurality of computing devices, a distributed computing system, or a computing network. Computer device 900 may be configured as a quantum computer, a classical computer, or a combination of quantum and classical computing functions.

[0066] In one example, the computer device 900 may include a processor 910 for performing processing functions associated with one or more features described herein. The processor 910 may include a single or multiple processors or a multi-core processor. In addition, the processor 910 may be implemented as an integrated processing system and / or a distributed processing system. The processor 910 may include a central processing unit (CPU), a quantum processing unit (QPU), a graphics processing unit (GPU), or a combination of these types of processors.

[0067] In one example, the computer device 900 may include a memory 920 for storing instructions executable by the processor 910 to perform the functions described herein. In one implementation, for example, the memory 920 may correspond to a computer-readable storage medium that stores code or instructions for performing one or more of the functions or operations described herein. In one example, the memory 920 may include one or more storage qubits.

[0068] In addition, the computer device 900 may include a communication component 930 that utilizes the hardware, software, and services described herein to establish and maintain communications with one or more parties. The communication component 930 may communicate between components on the computer device 900 and between the computer device 900 and external devices, such as devices located on a communication network and / or devices connected serially or locally to the computer device 900. For example, the communication component 930 may include one or more buses and may further include a transmit chain component and a receive chain component associated with a transmitter and a receiver, respectively, operable to interface with external devices. Aspects of the communication component 930 may be used to implement Figure 1 The multi-species ion trap network shown in .

[0069] In addition, computer device 900 may include data storage 940, which may be any suitable combination of hardware and / or software that provides mass storage of information, databases, and programs used in conjunction with the embodiments described herein. For example, data storage 940 may be a data repository for operating system 960 (e.g., a classical OS or a quantum OS). In one embodiment, data storage 940 may include memory 920.

[0070] The computer device 900 may also include a user interface component 950 that is operable to receive input from a user of the computer device 900 and may also be operable to generate output to be presented to the user or provided to a different system (directly or indirectly). The user interface component 950 may include one or more input devices, including but not limited to a keyboard, a numeric keypad, a mouse, a touch-sensitive display, a digitizer, navigation keys, function keys, a microphone, a voice recognition component, any other structure capable of receiving input from a user, or any combination thereof. In addition, the user interface component 950 may include one or more output devices, including but not limited to a display, a speaker, a tactile feedback mechanism, a printer, any other mechanism capable of presenting output to a user, or any combination thereof.

[0071] In one implementation, the user interface component 950 may send and / or receive messages corresponding to the operation of the operating system 960. In addition, the processor 910 may execute the operating system 960 and / or applications or programs, and the memory 920 or data storage 940 may store them.

[0072] When the computer device 900 is implemented as part of a cloud-based infrastructure solution, the user interface component 950 may be used to allow a user of the cloud-based infrastructure solution to interact remotely with the computer device 900 .

[0073] Computer device 900 may implement Figure 1One or more components or structures shown in the various types of ion trap networks in diagram 100, and Figure 7(a) , 7(b) and some or all of the components shown in 7(c). For example, communication component 930 may implement one or more of node 110, photon entangler 120, and / or wavelength converter 760.

[0074] Although the present disclosure is provided according to the illustrated embodiments, it will be readily appreciated by those skilled in the art that various modifications may be made to the embodiments and those modifications will be within the scope of the present disclosure. Therefore, those skilled in the art may make many modifications without departing from the scope of the appended claims.

Claims

1. A quantum networking node for use in a modular optical architecture for quantum computing, the quantum networking node comprising: Multiple storage qubits, each storage qubit based on 171 Yb + Atomic ions; and One or more communicating qubits, each based on 138 Ba + Atomic ions, wherein the plurality of storage qubits and the one or more communication qubits are part of a lattice in an atomic ion trap, and wherein the one or more communication qubits are located at one end of the lattice, at the other end of the lattice, or at both ends of the lattice, wherein the storage qubit and the communication qubit are composed of a pair of different ion species, a pair of different isotopes of the same species, a pair of different qubit basis states, or a combination thereof, and wherein the pair of different isotopes of the same kind has a Ba isotope different from a plurality of Ba isotopes including at least 138Ba, 137Ba and 133Ba.

2. The quantum networking node of claim 1 , wherein the storage qubit of one of the storage qubits 171 Yb + The atomic ion and one of the communication qubits 138 Ba + The local connection between the atomic ions is established by at least partially controlling the collective motion of the one storage qubit and the one communication qubit by an external laser field to couple the one storage qubit and the one communication qubit, the external laser field being configured to direct the collective motion of the one storage qubit to the one communication qubit. 171 Yb + Atomic ions and / or said one communicating qubit 138 Ba + Atomic ions exert forces.

3. The quantum networking node according to claim 2, wherein: The atomic ion trap is configured to receive a single laser, The second harmonic of the single laser corresponds to the 138 Ba + The first external laser field exerts a force on the atom and ion, and The third harmonic of the single laser corresponds to the 171 Yb + A second external laser field exerts force on the atoms and ions.

4. The quantum networking node of claim 3, wherein the second harmonic of the single laser is at an emission line at a wavelength of approximately 532 nanometers (nm), and wherein the third harmonic of the single laser is at an emission line at a wavelength of approximately 355 nm.

5. The quantum networking node according to claim 1, wherein: Said 171 Yb + Atomic ions are the first atomic species, Said 138 Ba + Atomic ions are the second atomic species, and The atomic mass of the first atomic species and the atomic mass of the second atomic species are substantially similar, and the atomic mass difference between the two atomic masses is less than 25%.

6. The quantum networking node according to claim 1, wherein: The one or more communication qubits include a plurality of communication qubits, and The quantum networking node is configured to multiplex between the plurality of communication qubits to enable repeated trials of photon emissions from the plurality of communication qubits.

7. The quantum networking node of claim 1, wherein the 138 Ba + The atomic ions are configured to emit photons by fluorescence, and the emitted photons are 138 Ba + Atomic ion entanglement.

8. A quantum networking node according to claim 7, wherein at least a portion of the spectrum of emitted photons is in the visible spectrum.

9. The quantum networking node of claim 7, wherein the emission line of the emitted photons is aligned with the emission line of the plurality of storage qubits. 171 Yb + Resonant isolation of atomic ions.

10. The quantum networking node of claim 9, wherein the emission lines include emission lines at wavelengths of approximately 493 nm and 650 nm, and wherein the 171 Yb + The resonance of the atomic ion is at a wavelength of approximately 369 nm.

11. The quantum networking node of claim 10, wherein the emission lines at wavelengths of approximately 493 nm and 650 nm correspond to the 138 Ba + The electronic ground-state energy level of the atomic ion Zeeman qubit state is connected to the excited state of visible light.

12. The quantum networking node of claim 1, wherein each storage qubit is configured to have a corresponding 171 Yb + Atomic ions 2 S 1 / 2 The ground state hyperfine level is encoded.

13. The quantum networking node according to claim 12, wherein the corresponding 171 Yb + The hyperfine state coherence time of atomic ions is about 1.5 seconds or longer.

14. The quantum networking node according to claim 12, wherein the corresponding 171 Yb + The splitting of the hyperfine qubit states of atomic ions is insensitive to magnetic field fluctuations.

15. The quantum networking node of claim 12, wherein each storage qubit is further configured for initialization and detection without shuttling a population of atomic states between hyperfine energy levels.

16. The quantum networking node of claim 1, wherein each communication qubit is configured to use the 138 Ba + Atomic ions 2 S 1 / 2 Ground state electron spin energy level.

17. The quantum networking node of claim 1, wherein the lattice is a linear lattice.

18. The quantum networking node of claim 1, wherein the one or more communication qubits comprises a plurality of communication qubits that are all located at the one end of the lattice, all located at the other end of the lattice, or some located at the one end of the lattice and the rest located at the other end of the lattice.

19. A quantum computing system having a modular optical architecture, the quantum computing system comprising: Multiple quantum networking nodes, each quantum networking node includes: Multiple storage qubits, each storage qubit based on 171 Yb + Atomic ions; and One or more communicating qubits, each based on 138 Ba + Atomic ions, wherein the plurality of storage qubits and the one or more communication qubits are part of a lattice in an atomic ion trap, and wherein the one or more communication qubits are located at one end of the lattice, at the other end of the lattice, or at both ends of the lattice; and a photon entangler coupled to each of the plurality of quantum networking nodes, wherein the storage qubit and the communication qubit are composed of a pair of different ion species, a pair of different isotopes of the same species, a pair of different qubit basis states, or a combination thereof, and wherein the pair of different isotopes of the same kind has a Ba isotope different from a plurality of Ba isotopes including at least 138Ba, 137Ba and 133Ba.

20. The quantum computing system of claim 19, wherein each storage qubit in each of the plurality of quantum networking nodes is configured to have a corresponding 171 Yb + Atomic Ions 2 S 1 / 2 The ground state hyperfine level is encoded.

21. The quantum computing system of claim 19, wherein each communication qubit in each of the plurality of quantum networking nodes is configured to use the 138 Ba + Atomic Ions 2 S 1 / 2 Ground state electron spin energy level.

22. The quantum computing system of claim 19, wherein a first communication qubit of the one or more communication qubits of a first quantum networking node of the plurality of quantum networking nodes is entangled with one of the one or more communication qubits of a second quantum networking node of the plurality of quantum networking nodes.

23. The quantum computing system of claim 22, wherein a second communication qubit of the one or more communication qubits of the first quantum networking node is entangled with one of the one or more communication qubits in a third quantum networking node of the plurality of quantum networking nodes.

24. The quantum computing system of claim 19, wherein the 138 Ba + The atomic ions are configured to emit photons by fluorescence, and the emitted photons are 138 Ba + Atomic ion entanglement.

25. A quantum computing system according to claim 24, wherein at least a portion of the spectrum of emitted photons is in the visible spectrum.

26. A quantum computing system according to claim 25, wherein the photon entangler is coupled to each of the plurality of quantum networking nodes via an optical fiber configured to operate on an optical communication spectrum, and the quantum computing system further comprises a wavelength converter to convert the visible spectrum of the emitted photons into the optical communication spectrum.

27. The quantum computing system of claim 26, wherein the optical communications spectrum includes wavelengths of approximately 1300-1550 nm.

28. A quantum computing system according to claim 26, wherein the photon entangler includes one or more optical components compatible with the optical communication spectrum.

29. The quantum computing system of claim 19, wherein the photon entangler comprises one or more reconfigurable optical switches to enable entanglement between any two quantum networking nodes from the plurality of quantum networking nodes.

30. The quantum computing system of claim 19, wherein the one or more communication qubits in each of the plurality of quantum networking nodes comprises a plurality of communication qubits that are all located at the one end of the lattice, all located at the other end of the lattice, or some located at the one end of the lattice and the rest located at the other end of the lattice.

31. A quantum networking node for use in a modular optical architecture for quantum computing, the quantum networking node comprising: multiple storage qubits; and one or more communicating qubits, wherein the plurality of storage qubits and the one or more communication qubits are part of a lattice in an atomic ion trap, and wherein the one or more communication qubits are located at one end of the lattice, at the other end of the lattice, or at both ends of the lattice, wherein the storage qubit and the communication qubit are composed of a pair of different ion species, a pair of different isotopes of the same species, a pair of different qubit basis states, or a combination thereof, and wherein the pair of different isotopes of the same kind has a Ba isotope different from a plurality of Ba isotopes including at least 138Ba, 137Ba and 133Ba.

32. A quantum networking node according to claim 31, wherein the pair of different ion species is one of Yb / Ba, Ca / Sr or Be / Mg.

33. The quantum networking node of claim 31 , wherein the pair of different ion species comprises one or more of Cd, Zn or Al.

34. The quantum networking node of claim 31, wherein: The pair of different ion species is Yb / Ba, The isotope of Yb is selected from a plurality of Yb isotopes including at least 171Yb, 174Yb, 176Yb and 172Yb, and The isotope of Ba is selected from a plurality of Ba isotopes including at least 138Ba, 137Ba or 133Ba.

35. The quantum networking node of claim 31 , wherein: The pair of different ion species is Ca / Sr, The isotope of Ca is selected from a plurality of Ca isotopes including at least 40Ca and 43Ca, and The isotope of Sr is selected from a plurality of Sr isotopes including at least 88Sr, 87Sr and 86Sr.

36. The quantum networking node of claim 31, wherein: The pair of different ion species is Be / Mg, The isotope of Be is 9Be, and The isotope of Mg is selected from a plurality of Mg isotopes including at least 24Mg, 25Mg and 26Mg.

37. The quantum networking node of claim 31, wherein the pair of different isotopes of the same species has a Yb isotope different from a plurality of Yb isotopes including at least 171Yb, 174Yb, 176Yb and 172Yb.

38. The quantum networking node of claim 31 , wherein the pair of different isotopes of the same species has a Ca isotope different from a plurality of Ca isotopes including at least 40Ca and 43Ca.

39. The quantum networking node of claim 31, wherein the pair of different isotopes of the same species has a different Sr isotope from a plurality of Sr isotopes including at least 88Sr, 87Sr, and 86Sr.

40. The quantum networking node of claim 31, wherein the pair of different isotopes of the same species has a Mg isotope different from a plurality of Mg isotopes comprising at least 24Mg, 25Mg, and 26Mg.

41. The quantum networking node of claim 31 , wherein the pair of different qubit basis states comprises two different qubit basis states from a hyperfine state, a Zeeman state, and an optical state.

42. The quantum networking node of claim 31 , wherein each of the plurality of storage qubits and each of the one or more communication qubits has a qubit basis state selected from a hyperfine state, a Zeeman state, or an optical state.

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