WO2025259337A2

WO2025259337A2 - Ytterbium-171 neutral atom-based quantum systems and methods

Info

Publication number: WO2025259337A2
Application number: PCT/US2025/019916
Authority: WO
Inventors: Jeffrey D. Thompson; Michael PEPER; Yiyi LI; Bichen Zhang; Genyue LIU; Pai Peng; Shuo MA
Original assignee: Princeton University
Current assignee: Princeton University
Priority date: 2024-03-14
Filing date: 2025-03-14
Publication date: 2025-12-18
Anticipated expiration: 2026-09-14
Also published as: WO2025259337A9; WO2025259337A3

Abstract

A quantum method includes providing a plurality of atoms including first and second ¹⁷¹Yb atoms spatially separated from one another and exciting the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state. A quantum logic gate includes a first ¹⁷¹Yb qubit excited to a target Rydberg state and a second ¹⁷¹Yb qubit spatially separated from the first ¹⁷¹Yb qubit, wherein the second ¹⁷¹Yb qubit is not excited to the target Rydberg state while the first ¹⁷¹Yb qubit is excited to the target Rydberg state. A quantum computing system includes a chamber housing a plurality of atoms including first and second ¹⁷¹Yb atoms spatially separated from one another and at least one gate laser source configured to excite the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state.

Description

YTTERBIUM-171 NEUTRAL ATOM-BASED QUANTUM SYSTEMS AND METHODS

CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This application claims the benefit of, and priority to, U.S. Provisional Patent Application No. 63/565,409, filed on March 14, 2024, the entire contents of which are hereby incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH I DEVELOPMENT

[0002] This invention was made with government support under Grant No. W91 1NF-18-1- 0215 awarded by the Army Research Office, Grant No. N00014-201-2426 awarded by the Office of Naval Research, Grant No. W91 INF-20- 1-0021 awarded by the Defense Advanced Research Projects Agency, and Grant No. 0MA2120757 awarded by the National Science Foundation. The government has certain rights in the invention.

FIELD

[0003] The present disclosure relates to quantum technologies and, more specifically, to ¹⁷¹Yb neutral atom-based quantum systems and methods utilizing ¹⁷¹Yb atoms excited to specific Rydberg states.

BACKGROUND

[0004] Entangling gates are utilized in neutral atom quantum computing to create entangled states between neutral atom qubits by exciting the qubits to higher energy levels called Rydberg states. Two qubits in Rydberg states experience a strong interaction (called the Rydberg blockade), which is the basis for generating entanglement between the qubits.

[0005] Most neutral atom quantum computers use alkali atoms (e.g., Rb, Cs, etc.) due to their simple energy level structures, whereby the interactions between Rydberg states are well- understood and predictable. Such neutral atom quantum computers have been demonstrated to achieve entangling gates with low error rates (e.g., quantum state fidelities of F ~ 0.995).

[0006] However, using lanthanides such as Ytterbium-171 (¹⁷¹Yb) are far less predictable and, as a result, have higher error rates. The Rydberg states of ¹⁷¹Yb are highly complex, and known techniques for entangling gates using ¹⁷¹Yb have demonstrated quantum state fidelities of only F

~ 0.980. SUMMARY

[0007] To the extent consistent, any of the aspects detailed below may be used in conjunction with any or all of the other aspects detailed hereinbelow.

[0008] Provided in accordance with aspects of the present disclosure is a ¹⁷¹Yb neutral atombased quantum method including providing a plurality of atoms including first and second ¹⁷¹Yb atoms spatially separated from one another and exciting the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state.

[0009] In an aspect of the present disclosure, the target Rydberg state is free of Forster resonances.

[0010] In another aspect of the present disclosure, the target Rydberg state is a 6sns F = 1/2 state with an effective principal quantum number, n, of from 40 to 70.

[0011] In still another aspect of the present disclosure, the target Rydberg state is a triplet- connected Rydberg state.

[0012] In yet another aspect of the present disclosure, the target Rydberg state satisfies the inequality did? < (n²eao)²/lOOO, where di is a dipole matrix clement from the target Ryberg state to a first state of a pair of opposite-parity Rydberg states, d? is a dipole matrix element from the target Ryberg state to a second state of the pair of opposite-parity Rydberg states, n is an effective principal quantum number of the target Ryberg state, e is an electron charge and ao is the Bohr radius, for all opposite-parity Rydberg states within 500 MHz of the target state.

[0013] In still yet another aspect of the present disclosure, the method further includes adjusting at least the first ¹⁷¹Yb atom (and, in aspects, both the first and second ¹⁷¹Yb atoms) from an initial state to a pre-excited state. In such aspects, exciting the first ¹⁷¹Yb atom to the target Rydberg state includes exciting the first ¹⁷¹ Yb atom from the pre-excited state to the target Rydberg state.

[0014] In another aspect of the present disclosure, the pre-excited state is a 3P0 metastable state. Additionally or alternatively, the initial state is a ISO ground state.

[0015] In another aspect of the present disclosure, the spatial separation between the first and second ¹⁷¹Yb atoms is at most 10 pm.

[0016] In yet another aspect of the present disclosure, a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹Yb atoms is at least 0.994. [0017] In still another aspect of the present disclosure, the method further includes measuring a statc-dcpcndcnt fluorescence from the plurality of atoms. In such aspects, the method may also include determining a population of atoms of the plurality of atoms in a pre-determined energy state based on the state-dependent fluorescence.

[0018] A ¹⁷¹Yb neutral atom-based quantum logic gate provided in accordance with the present disclosure includes a first ¹⁷¹Yb qubit excited to a target Rydberg state and a second ¹⁷¹Yb qubit spatially separated from the first ¹⁷¹Yb qubit, wherein the second ¹⁷¹Yb qubit is not excited to the target Rydberg state while the first ¹⁷¹Yb qubit is excited to the target Rydberg state.

[0019] In aspects of the present disclosure, the target Rydberg state may be configured according to any of the aspects detailed above or otherwise herein.

[0020] In aspects of the present disclosure, the ¹⁷¹Yb neutral atom-based quantum logic gate may include a spatial separation between the first and second ¹⁷¹Yb qubits of at most 10 pm and/or a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹ Yb qubits of at least 0.994.

[0021] A quantum computing system provided in accordance with aspects of the present disclosure includes a chamber housing a plurality of atoms including first and second ¹⁷¹ Yb atoms spatially separated from one another, and at least one gate laser source configured to excite the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state if the first ¹⁷¹Yb atom is already excited to the target Rydberg state.

[0022] In an aspect of the present disclosure, the system further includes at least one preparation laser source configured to trap the first and second ¹⁷¹Yb atoms in an optical trap.

[0023] In another aspect of the present disclosure, the system further includes an optical pumping system configured to adjust the first and second ¹⁷¹ Yb atoms from an initial state to a preexcited state. In such aspects, the at least one gate laser source is configured to excite the first ¹⁷¹ Yb atom from the pre-excited state to the target Rydberg state.

[0024] In aspects of the present disclosure, the pre-excited state is a 3P0 metastable state and/or the initial state is a ISO ground state.

[0025] In still another aspect of the present disclosure, the system further includes an optical detector configured to measure a state-dependent fluorescence of the plurality of atoms. Further, in aspects, the system also includes a controller configured to determine a population of atoms of the plurality of atoms in a pre-determined energy state based on the state-dependent fluorescence. [0026] In aspects of the present disclosure, the quantum computing system may include a spatial separation between the first and second ¹⁷¹Yb atoms of at most 10 pm and/or a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹Yb atoms of at least 0.994.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Various aspects and features of the present disclosure are described hereinbelow with reference to the drawings wherein:

[0028] FIG. 1 is an energy level diagram of the Rydberg states of ¹⁷¹Yb;

[0029] FIG. 2 is schematic illustration of an exemplary architecture for a ¹⁷¹Yb neutral atombased quantum computer in accordance with the present disclosure; and

[0030] FIG. 3 is a flow diagram of a ¹⁷¹Yb neutral atom-based quantum method in accordance with aspects of the present disclosure.

DETAILED DESCRIPTION

[0031] The present disclosure provides systems and methods for ¹⁷¹ Yb neutral atom-based quantum systems and methods with improved , a quantum gate fidelity of a gate operation acting on two or more ¹⁷¹ Yb atoms by exciting one or more of the ¹⁷¹ Yb atoms from a pre-excited energy state to a target Rydberg state. Exciting one or more of the ¹⁷¹Yb atoms to target Rydberg states in accordance with the present disclosure overcomes the complicated interaction potential and weak Rydberg blockade challenges that have plagued conventional approaches to ¹⁷¹Yb neutral atom-based quantum systems and methods. Indeed, the present disclosure achieves quantum state fidelities between two or more ¹⁷¹Yb atoms of, in aspects, at least 0.990; in other aspects, at least 0.991; in still other aspects, at least 0.992; in yet other aspects, at least 0.993; and, in still yet other aspects, at least 0.994.

[0032] FIG. 1 illustrates the energy level diagram for ¹⁷¹Yb, indicating Rydberg series converging to the two hyperfine states of the ¹⁷¹ Yb⁺ (6s)² S1/2 ground state. For simplicity, channels converging to electronically excited states of the ion core, are neglected. The series are labeled by their good quantum numbers F and parity (labelled as e or o).

[0033] Neutral atom-based quantum systems and methods, such as those utilizing ¹⁷¹Yb atoms, are implemented by exciting the atoms for a short period of time to a Rydberg state. However, when two (or more) atoms are near each other and both in the same state, both atoms cannot be excited to the Rydberg state due to the strong interactions between the atoms, referred to as Rydberg blockade. Leveraging this Rydberg blockade enables the creation of controlled interactions between qubits such as, for example, implementation of quantum logic gates with two or more qubits. Leveraging the Rydberg blockade in this manner is not only applicable to quantum computing, but also has applications in quantum simulation, quantum communication, and quantum sensing, for example. Thus, while the aspects and features of the present disclosure are exemplified herein with respect to quantum logic gates for quantum computing, the present disclosure is not limited thereto as the aspects and features of the present disclosure are also applicable to, for example and without limitation, quantum simulation, quantum communication, and quantum sensing.

[0034] The Rydberg blockade, however, can be limited or weakened and, in such cases, errors can arise, if the strength of the interaction between two Rydberg atoms is not sufficiently large to completely prevent excitation of both atoms to the Rydberg state. More specifically, it has been found in accordance with the present disclosure that certain Rydberg states of ¹⁷¹Yb atoms limit the achievement of the Rydberg blockade. In particular, the 65'745' and 6s59s F=3/2 Rydberg states of ¹⁷¹Yb atoms have the unusual property that the energy of these states is within several MHz of the average energy of nearby opposite-parity Rydberg states with quantum numbers {6snp F = 3/2, (>sn'p F = 5/2], where n and rf are close to 74 or 59. Indeed, this applies to all 6sns F = 3/2 states with n between 40 and 110. The difference in energy between the 6sns state and the average of the 6snp states is called the Forster defect, and when it is small compared to the interaction strength, a Forster resonance is said to occur. Near Forster resonances, strong mixing occurs between the 6sns states and the opposite parity 6snp states, giving rise to complicated interaction potentials that cannot be captured by a simple 1/R⁶ dependence at small separations. This, in turn, gives rise to eigenstates of the interaction potential with very little energy shift even at very small separation. This spoils the Rydberg blockade and causes gate errors. Further, the Forster resonance enhances the interaction strength at large distances, by increasing the coefficient of the long-range I//?⁶ interaction. This increases the required separation between qubits used for two (or more) qubit quantum logic gates (also referred to as entangling gates) or other multi-qubit applications. In addition, the Forster resonance makes the interactions anisotropic with respect to the angle between the axis connecting the atoms and the quantization axis (e.g., the axis of the magnetic field), which can limit the qubit connectivity in an array. [0035] It has further been found in accordance with the present disclosure that while certain Rydberg states of ¹⁷¹Yb atoms, such as those detailed above, have properties that decrease the fidelity of quantum logic gates, other Rydberg states of ¹⁷¹Yb atoms do not have the same properties. That is, as determined in accordance with the present disclosure, Rydberg states of ¹⁷¹Yb atoms of the form 6sns F = 1/2 do not have small Forster defects (e.g., they are free of Forster resonances). There are two 6sns F = 1/2 series, which are described by whether they connect to the mostly singlet ('So) or mostly triplet (³Si) states at low principal quantum number, n. As utilized herein, Rydberg states of ¹⁷¹ Yb atoms are considered to be triplet-connected if they are pail of a series that is predominantly ³Si in character at low principal quantum number and are considered to be singlet-connected if they are part of a series that is predominantly 'So in character at low principal quantum number.

[0036] Triplet-connected 6sns F = 1/2 Rydberg states of ¹⁷¹Yb atoms in particular, and at many principal quantum numbers, n, have strong Rydberg blockade. Further, transitions to these triplet-connected 6sns F = 1/2 Rydberg states of ¹⁷¹Yb atoms can be driven efficiently from the ³P0 level because of their triplet character.

[0037] Thus, in accordance with the present disclosure, 6sns F- 1/2 Rydberg states of ¹⁷¹Yb atoms and, in particular aspects, triplet-connected 6sns F=l/2 Rydberg states of ¹⁷¹ Yb atoms, are utilized to achieve higher fidelity in quantum logic gate operations and/or other quantum applications. Further, 6sns F=l/2 Rydberg states of ¹⁷¹Yb atoms (and, in particular aspects, triplet-connected 6sns F=l/2 Rydberg states of ¹⁷¹Yb atoms) enable quantum operations, e.g., parallel gate operations, with higher spatial density, e.g., a spacing of 10 pm or less between ¹⁷¹Yb atoms.

[0038] Turning to FIG. 2, an exemplary ¹⁷¹Yb neutral atom-based quantum computer 100 configured for use with the aspects and features of the present disclosure is shown generally including a chamber 110, e.g., an ultra-high vacuum (UHV) chamber; a plurality of qubits 120, e.g., an array of spatially separated ¹⁷¹ Yb atoms, disposed within the chamber 110; one or more preparation laser sources 130 for cooling, transporting, and/or trapping the plurality of qubits 120; one or more gate laser and/or radiofrequency sources 140 for performing logic gate operations; a detector 150, e.g., a camera or other suitable optical detector, for measuring the logic gate operation results; modulation components 160 configured to, for example, modulate the outputs of the laser and/or radiofrequency sources 140 in time and/or space; a quantum-side controller 170 for controlling the modulation components 160 and receiving the measured logic gate operation results from detector 150; and a classical- side controller 180 configured to communicate with the quantum-side controller 170, provide a user interface for an operator, and perform optimization, data analysis, and the like.

[0039] Each qubit of the plurality of qubits may be, as noted above, a ¹⁷¹Yb atom and may be encoded as a qubit in internal degrees of freedom of the ¹⁷¹Yb atom. The encoding may be based on the nuclear spin and electronic states of the ¹⁷¹Yb atom. The plurality of qubits 120 may include an array of less than 100 qubits. In other aspects, the plurality of qubits 120 includes an array of at least 100 qubits. The array may be a ID array, a 2D array, or a 3D array. In aspects, one or more of the atoms are trapped in an optical trap.

[0040] The plurality of qubits, in aspects, cooperate to form one or more quantum logic gates. For example, a quantum logic gate may include at least first and second ¹⁷¹ Yb atoms each defining a qubit and spatially separated from the other. In aspects, the first and second qubits are separated by a distance of up to 10 pm, up to 9 pm, up to 8 pm, up to 7 pm, up to 6 pm, up to 5 pm, or up to 4 pm and/or may be separated by a distance of at least 1 pm, at least 2 pm, at least 3 pm, at least 4 pm, at least 5 pm, at least 6 pm, at least 7 pm, or at least 8 pm, including any ranges or subranges thereof.

[0041] In aspects, the plurality of qubits 120 may be transferred into the chamber 110 from a reservoir of laser cooled atoms at < 10 pK temperature. One or more of the preparation laser sources 130 may function as optical traps to trap one or more qubits of the plurality of qubits 120, e.g., in an optical tweezer or an optical lattice, wherein “optical tweezer” refers a highly-focused laser that uses the three-dimensional optical gradient force as the physical principle and wherein “optical lattice” refers to a spatially periodic polarization pattern formed by the interference of counter-propagating laser beams.

[0042] One or more of the preparation laser sources 130 may additionally or alternatively function as an optical pumping system configured to prepare one or more qubits of the plurality of qubits 120, e.g., qubits in the one or more optical traps, into a pre-excited energy state. The optical pumping system, more specifically, may be configured to transition one or more qubits of the plurality of qubits 120 from an initial energy state, e.g., a ISO ground state, to the pre-excited energy state, e.g., a 3P0 metastable state. Detector 150 may be utilized to detect the initial energy state and/or to confirm the pre-excited energy states of the one or more qubits of the plurality of qubits 120.

[0043] As noted above, the one or more gate laser and/or microwave sources 140 enable logic gate operations with the results of these logic gate operations measured by the detector 150, e.g., a camera or other suitable optical detector configured to measure a state-dependent fluorescence of the qubits. More specifically, the one or more gate laser and/or microwave sources 140 may excite one or more qubits of the plurality of qubits 120 from the pre-excited energy state to a target Rydberg state. As detailed above, target Rydberg states in accordance with the present disclosure are free of Forster resonances and may be 6sns F=l/2 states that are, in aspects, triplet-connected 6sns F= 1/2 Rydberg states of ¹⁷¹Yb atoms. The effective principal quantum number, n. of these target Rydberg states may be, in aspects, from 40 to 70; in other aspects, from 50 to 60; and, in still other aspects, from 54 to 55. In aspects, the target Rydberg state is a 6sns F = ^l/i state, where the effective principal quantum number, n, is 40.45, 42.44, 46.39, 47.38, 48.37, 52.31, 53.30, 54.28, 55.27, 56.25, 62.14, 63.11, 64.09, or 67.02, including variations of up to plus or minus 10% to account for tolerances, rounding, and/or other factors.

[0044] Continuing with the above example, the one or more gate laser and/or microwave sources 140 may excite a first ¹⁷¹Yb atom of the pair of first and second ¹⁷¹Yb atoms from the preexcited energy state to a target Rydberg state in accordance with the present disclosure, achieving a , a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹Yb atoms of, in aspects, at least 0.990; in other aspects, at least 0.991; in still other aspects, at least 0.992; in yet other aspects, at least 0.993; and in still yet other aspects, at least 0.994.

[0045] In aspects, even where the one or more gate laser and/or radiofrequency sources 140 would otherwise excite both the first and second ¹⁷¹Yb atoms to a target Rydberg state, the interaction between the first and second ¹⁷¹Yb atoms (e.g., the Rydberg blockade) prevents both atoms from being excited simultaneously to the target Rydberg state. Thus, only one of the first or second ¹⁷¹Yb atoms is excited to the target Rydberg state.

[0046] The quantum-side controller 170, as noted above, receives the measured logic date operation results, which may include state-dependent fluorescence information. Based on this state-dependent fluorescence information measured from detector 150, the quantum-side controller 170 and/or the classical-side controller 180 may determine a population of qubits in the pre-excited energy state. [0047] Although ¹⁷¹Yb neutral atom-based quantum computer 100 is detailed above with respect to quantum logic gates based on two qubits, it is understood that the aspects and features of ¹⁷¹Yb neutral atom-based quantum computer 100 detailed above, as well as of the methods of the present disclosure detailed below, are likewise applicable to quantum logic gate operations between three or more qubits. In addition, as noted above, the aspects and features of the present disclosure of exciting only one (or some) ¹⁷¹Yb atoms to a target Rydberg state without exciting another (or some other) ¹⁷¹ Yb atoms to the target Rydberg state may find applicability to other quantum systems and methods other than quantum computing.

[0048] Methods provided in accordance with the present disclosure are detailed below. The methods detailed below may be implemented using ¹⁷¹Yb neutral atom-based quantum computer 100 (FIG. 2), or another quantum computer. Further, although detailed below with respect to improving fidelity of gate operations in a two (or more) ¹⁷¹ Yb atom quantum logic gate, the method detailed below may likewise be implemented in other quantum systems such as, for example, for quantum simulation, quantum communication, and/or quantum sensing systems.

[0049] Referring to FIG. 3, method 300 begins at step 310 wherein a plurality of spatially separated ¹⁷¹Yb atoms are provided, including at least a first ¹⁷¹Yb atom and a second ¹⁷¹Yb atom. Each atom may be encoded in internal degrees of freedom of the atom to define a qubit. The encoding may be based on the nuclear spin and electronic states of the qubit. The spacing between at least the first and second atoms may be a distance of up to 10 pm, up to 9 pm, up to 8 pm, up to 7 pm, up to 6 pm, up to 5 pm, or up to 4 pm and/or a distance of at least 1 pm, at least 2 pm, at least 3 pm, at least 4 pm, at least 5 pm, at least 6 pm, at least 7 pm, or at least 8 pm, including any ranges or subranges thereof. The plurality of atoms may include an array of less than 100 atoms. The plurality of atoms may include an array of at least 100 atoms. The array may be a ID array, a 2D array, or a 3D array. In aspects, one or more of the atoms, e.g., the first and second atoms, are trapped in an optical trap.

[0050] As indicated at step 320, method 300 further includes adjusting a state of at least the first ¹⁷¹Yb atom from an initial state to a pre-excited energy state. The initial state may be a ISO ground state or other suitable state. One or more detectors, e.g., a camera or other suitable optical detector, may be utilized to detect the initial state of the atom(s) adjusted from an initial state to a pre-excited energy state. The pre-excited energy state may be a 3P0 metastable state or other suitable state and may likewise be confirmed using the one or more detectors. The above-detailed state adjustment may be performed, in aspects, using an optical pumping system.

[0051] Method 300 further includes, as indicated at step 330, exciting at least the first ¹⁷¹Yb atom from the pre-excited energy state to a target Rydberg state without exciting one or more other atoms, e.g., the second ¹⁷¹Yb atom, if the first ¹⁷¹Yb atom is excited to the target Rydberg state. The target Rydberg state may be free of Forster resonances. The target Rydberg state may be a 6sns F = Vi state, where the effective principal quantum number, n, is, in aspects, from 40 to 70; in other aspects, from 50 to 60; and, in still other aspects, from 54 to 55. The Rydberg state may be a triplet-connected Rydberg state. In aspects, the target Rydberg state is a 6sns F = 1 state, where the effective principal quantum number, n, is about 40.45, 42.44, 46.39, 47.38, 48.37, 52.31, 53.30, 54.28, 55.27, 56.25, 62.14, 63.11, 64.09, or 67.02, wherein the term “about” as utilized herein encompasses variations of up to plus or minus 10% to account for tolerances, rounding, and/or other factors.

[0052] Exciting at least the first ¹⁷¹Yb atom from the pre-excited energy state to the target Rydberg state may include, for example, attempting to excite both the first and second ¹⁷¹Yb atoms, altematingly exciting the first and second ¹⁷¹ Yb atoms, or utilizing any other suitable approach for exciting one or more atoms to a target Rydberg state in accordance with the present disclosure.

[0053] Also provided in accordance with the present disclosure is a method for identifying target Rydberg states, e.g., Rydberg states that are free of Forster resonances, for use in a quantum system to achieve the above-detailed aspects and features of the present disclosure. This may be accomplished by determining an absence of Forster resonances based on the absence of pairs of opposite-parity Rydberg states with large dipole matrix elements to the target state, and with energy within 500 MHz of the target state. A pair state can be said to have a large matrix element to the target state when the inequality dic/2 < (n²eao)²/lOOO is satisfied, where di is the dipole matrix element from the target state to the first state in the pair, dz is the dipole matrix element from the target state to the other state in the pair, n is the effective principal quantum number of the target state, e is the electron charge and ao is the Bohr radius (approximately 5.29 x 10'¹¹ meters). The expression n²eao is a typical order of magnitude for a dipole matrix element between opposite parity states, and the factor of 1000 imposes a cutoff that allows opposite-parity states with small matrix elements to be ignored. [0054] There are no Rydberg states of the form 6sns F=3/2 that satisfy the above condition for n from 40 to 100. However, this condition is satisfied by certain triplct-conncctcd Rydberg states of the form 6sns F=l/2. More specifically, in the range of n = 40 to 70, this condition is satisfied by states with effective principal quantum numbers (rounded to two decimal places) including 40.45, 42.44, 46.39, 47.38, 48.37, 52.31, 53.30, 54.28, 55.27, 56.25, 62.14, 63.11, 64.09, 67.02.

[0055] It should be understood that the foregoing description is only illustrative of the present disclosure. Various alternatives and modifications can be devised by those skilled in the art without departing from the disclosure. Accordingly, the present disclosure is intended to embrace all such alternatives, modifications, and variances. The aspects described with reference to the attached drawings are presented only to demonstrate certain examples of the disclosure. Other elements, steps, methods, and techniques that are insubstantially different from those described above and/or in the appended claims are also intended to be within the scope of the disclosure.

Claims

WHAT IS CLAIMED IS:

1. A ¹⁷¹ Yb neutral atom-based quantum method, comprising: providing a plurality of atoms including a first ¹⁷¹Yb atom and a second ¹⁷¹Yb atom spatially separated from the first ¹⁷¹Yb atom; and exciting the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state.

2. The method according to claim 1 , wherein the target Rydberg state is free of Forster resonances .

3. The method according to claim 1, wherein the target Rydberg state is a 6sns F = 1/2 state with an effective principal quantum number, n, of from 40 to 70.

4. The method according to claim 1, wherein the target Rydberg state is a triplet-connected Rydberg state.

5. The method according to claim 1, wherein the target Rydberg state satisfies the inequality didi < (n²eao)²/lOOO, where di is a dipole matrix element from the target Ryberg state to a first state of a pair of opposite-parity Rydberg states, di is a dipole matrix element from the target Ryberg state to a second state of the pair of opposite -parity Rydberg states, n is an effective principal quantum number of the target Ryberg state, e is an electron charge and ao is the Bohr radius, for all opposite-parity Rydberg states within 500 MHz of the target state.

6. The method according to claim 1, further comprising: adjusting the first ¹⁷¹Yb atom from an initial state to a pre-excited state, wherein exciting the first ¹⁷¹Yb atom to the target Rydberg state includes exciting the first ¹⁷¹ Yb atom from the pre-excited state to the target Rydberg state.

7. The method according to claim 6, wherein the pre-excited state is a 3P0 metastable state.

8. The method according to claim 7, wherein the initial state is a ISO ground state.

9. The method according to claim 1 , wherein the spatial separation between the first and second ¹⁷¹Yb atoms is at most 10 pm.

10. The method according to claim 1, wherein a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹ Yb atoms is at least 0.994.

11. The method according to claim 1, further comprising measuring a state-dependent fluorescence from the plurality of atoms.

12. The method according to claim 11, further comprising determining a population of atoms of the plurality of atoms in a pre-determined energy state based on the state-dependent fluorescence.

13. A ¹⁷¹Yb neutral atom-based quantum logic gate, comprising: a first ¹⁷¹Yb qubit excited to a target Rydberg state; and a second ¹⁷¹Yb qubit spatially separated from the first ¹⁷¹Yb qubit, wherein the second ¹⁷¹Yb qubit is not excited to the target Rydberg state while the first ¹⁷¹ Yb qubit is excited to the target Rydberg state.

14. The quantum logic gate according to claim 13, wherein the target Rydberg state is free of Forster resonances.

15. The quantum logic gate according to claim 13, wherein the target Rydberg state is a 6sns F = 1/2 state with an effective principal quantum number, n, of from 40 to 70.

16. The quantum logic gate according to claim 13, wherein the target Rydberg state is a triplet- connected Rydberg state.

17. The quantum logic gate according to claim 13, wherein the target Rydberg state satisfies the inequality didi < (n²eao)²/lOOO, where di is a dipole matrix element from the target Ryberg state to a first state of a pair of opposite-parity Rydberg states, di is a dipole matrix element from the target Ryberg state to a second state of the pair of opposite-parity Rydberg states, n is an effective principal quantum number of the target Ryberg state, e is an electron charge and ao is the Bohr radius, for all opposite-parity Rydberg states within 500 MHz of the target state.

18. The quantum logic gate according to claim 13, wherein the spatial separation between the first and second ¹⁷¹Yb qubits is at most 10 pm.

19. The quantum logic gate according to claim 13, wherein a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹Yb qubits is at least 0.994.

20. A quantum computing system, comprising: a chamber housing a plurality of atoms including a first ¹⁷¹Yb atom and a second ¹⁷¹Yb atom spatially separated from the first ¹⁷¹Yb atom; and at least one gate laser source configured to excite the first ¹⁷¹Yb atom to a target Rydberg state without exciting the second ¹⁷¹Yb atom to the target Rydberg state if the first atom is already in the target Rydberg state.

21. The quantum computing system according to claim 20, further comprising at least one preparation laser source configured to trap the first and second ¹⁷¹Yb atoms in an optical trap.

22. The quantum computing system according to claim 20, further comprising an optical pumping system configured to adjust the first and second ¹⁷¹Yb atoms from an initial state to a prc-cxcitcd state, and wherein the at least one gate laser source is configured to excite the first ¹⁷¹Yb atom from the pre-excited state to the target Rydberg state.

23. The quantum computing system according to claim 22, wherein the pre-excited state is a 3P0 metastable state.

24. The quantum computing system according to claim 22, wherein the initial state is a ISO ground state.

25. The quantum computing system according to claim 20, further comprising an optical detector configured to measure a state-dependent fluorescence of the plurality of atoms.

26. The quantum computing system according to claim 25, further comprising a controller configured to determine a population of atoms of the plurality of atoms in a pre-determined energy state based on the state-dependent fluorescence.

27. The quantum computing system according to claim 20, wherein the spatial separation between the first and second ¹⁷¹Yb atoms is at most 10 pm.

28. The quantum computing system according to claim 20, wherein a quantum gate fidelity of a gate operation acting on the first and second ¹⁷¹Yb atoms is at least 0.994.

29. The quantum computing system according to claim 20, wherein the target Rydberg state is free of Forster resonances.

30. The quantum computing system according to claim 20, wherein the target Rydberg state is a 6sns F = 1/2 state with an effective principal quantum number, n, of from 40 to 70.

31. The quantum computing system according to claim 20, wherein the target Rydberg state is a triplet-connected Rydberg state.

32. The quantum computing system according to claim 20, wherein the target Rydberg state satisfies the inequality didi < (n²eao)²/lOOO, where di is a dipole matrix element from the target Ryberg state to a first state of a pair of opposite -parity Rydberg states, di is a dipole matrix element from the target Ryberg state to a second state of the pair of opposite-parity Rydberg states, n is an effective principal quantum number of the target Ryberg state, e is an electron charge and ao is the Bohr radius, for all opposite-parity Rydberg states within 500 MHz of the target state.