Quantum memory using a hybrid circuit with flux qubits and nitrogen-vacancy centers

Lü, Xin-You; Xiang, Ze-Liang; Cui, Wei; You, J. Q.; Nori, Franco

doi:10.1103/physreva.88.012329

Cited by 89 publications

(74 citation statements)

References 58 publications

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“…The simultaneous eigenstates of J z and J 2 are known as the Dicke states and when such an ensemble is restricted to the N + 1 dimensional subspace which is symmetric with respect to qubit exchange it may be considered to be a d = N + 1-dimensional qudit with a basis given by the symmetric Dicke states of the ensemble. Indeed, there have been proposals for qubit ensembles to be coupled to computational qubits in the context of utilizing the collective ensemble states as a quantum memory [52][53][54][55]. A particularly promising candidate for such an ensemble-qubit hybrid system is in the coupling of an NV center ensemble in diamond to a flux qubit with coherent coupling between such systems having been experimentally demonstrated [34] and we will return to this later.…”

Section: Methodsmentioning

confidence: 99%

“…Only one value of the parameter φ is required to create displacements in both quadratures as U † · e iθJ x · U = e iθJ y with U = (R(π/2)H ) ⊗N . As we have already mentioned, a particular promising hybrid system in which to realize an ensemble-qubit coupling is with an ensemble of NV centers coupled to a superconducting flux qubit, such as in the proposals of [53,54]. Such a coupling has been experimentally realized [34] with a coupling term of the form,…”

Section: Methodsmentioning

confidence: 99%

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Quantum computation mediated by ancillary qudits and spin coherent states

2015

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Publisher's copyright statement:Reprinted with permission from the American Physical Society: Physical Review A 91, 012308 c (2015) by the American Physical Society. Readers may view, browse, and/or download material for temporary copying purposes only, provided these uses are for noncommercial personal purposes. Except as provided by law, this material may not be further reproduced, distributed, transmitted, modied, adapted, performed, displayed, published, or sold in whole or part, without prior written permission from the American Physical Society.Additional information: Use policyThe full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that:• a full bibliographic reference is made to the original source • a link is made to the metadata record in DRO • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders.Please consult the full DRO policy for further details. Models of universal quantum computation in which the required interactions between register (computational) qubits are mediated by some ancillary system are highly relevant to experimental realizations of a quantum computer. We introduce such a universal model that employs a d-dimensional ancillary qudit. The ancilla-register interactions take the form of controlled displacements operators, with a displacement operator defined on the periodic and discrete lattice phase space of a qudit. We show that these interactions can implement controlled phase gates on the register by utilizing geometric phases that are created when closed loops are traversed in this phase space. The extra degrees of freedom of the ancilla can be harnessed to reduce the number of operations required for certain gate sequences. In particular, we see that the computational advantages of the quantum bus (qubus) architecture, which employs a field-mode ancilla, are also applicable to this model. We then explore an alternative ancilla-mediated model which employs a spin ensemble as the ancillary system and again the interactions with the register qubits are via controlled displacement operators, with a displacement operator defined on the Bloch sphere phase space of the spin coherent states of the ensemble. We discuss the computational advantages of this model and its relationship with the qubus architecture.

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Section: Methodsmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

Quantum computation mediated by ancillary qudits and spin coherent states

2015

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“…1(a)]. We use NV centers in a diamond crystal as a spin ensemble [22]. Each flux qubit is realized by a superconducting loop interrupted with three Josephson junctions and biased by a static external magnetic field perpendicular to the loop [38].…”

Section: Systemmentioning

confidence: 99%

“…Recently, hybrid quantum systems [13][14][15][16][17][18][19][20][21][22][23][24][25] have been strongly recommended for quantum simulation because they can combine two distinct advantages of the subsystems: the tunability of artificial atoms such as quantum circuits, and the long coherence times of atoms or spins. Also, strong and tunable coupling between two subsystems can be realized via either direct [19,[26][27][28] or indirect [29][30][31] coupling schemes.…”

Section: Introductionmentioning

confidence: 99%

Coupling spin ensembles via superconducting flux qubits

et al. 2014

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We study a hybrid quantum system consisting of spin ensembles and superconducting flux qubits, where each spin ensemble is realized using the nitrogen-vacancy centers in a diamond crystal and the nearest-neighbor spin ensembles are effectively coupled via a flux qubit. We show that the coupling strengths between flux qubits and spin ensembles can reach the strong and even ultrastrong coupling regimes by either engineering the hybrid structure in advance or tuning the excitation frequencies of spin ensembles via external magnetic fields. When extending the hybrid structure to an array with equal coupling strengths, we find that in the strong-coupling regime, the hybrid array is reduced to a tight-binding model of a one-dimensional bosonic lattice. In the ultrastrong-coupling regime, it exhibits quasi-particle excitations separated from the ground state by an energy gap. Moreover, these quasi-particle excitations and the ground state are stable under a certain condition that is tunable via the external magnetic field. This may provide an experimentally accessible method to probe the instability of the system.

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“…Such memory is one of the basic building blocks for the future large-scale quantum information processing tasks, including scalable quantum computation and long-distance quantum communication. For this purpose, a lot of efforts have been made to combine the advantages of different kinds of quantum systems for building hybrid quantum devices [4][5][6][7], including using ultracold atomic ensembles [8,9], nitrogen-vacancy center ensemble [10][11][12][13][14], and spin ensembles [15,16] coupled with superconducting qubit by transmission line. In the hybrid systems, solid-state elements [1,2] are suitable for engineering the processors, and microscopic systems with long coherence times can be proposed as possible quantum memories.…”

Section: Introductionmentioning

confidence: 99%

Robust quantum storage and retrieval in a hybrid system by controllable Stark-chirped rapid adiabatic passages

Feng

Dong

et al. 2015

Quantum Inf Process

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Quantum memory is one of the basic building blocks in large-scale quantum computers. In the paper, we propose a scheme to realize a quantum memory in a hybrid system by controllable Stark-chirped rapid adiabatic passages. In the hybrid system, by taking advantage of long coherence times in microscopic system, which is a twolevel system naturally embedded in a current-biased Josephson junction, individual two-level system can be regarded as a quantum memory. The scheme of storage and retrieval is realized by Stark-chirped rapid adiabatic passages, which is insensitive to the details of the applied adiabatic pulses. In numerical investigation of the storage process using adiabatic master equations, we demonstrate that high-fidelity quantum memory can be achieved under practical noises. Finally, the experimental feasibility and performance are discussed based on the current experimental status.

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Quantum memory using a hybrid circuit with flux qubits and nitrogen-vacancy centers

Cited by 89 publications

References 58 publications

Quantum computation mediated by ancillary qudits and spin coherent states

Quantum computation mediated by ancillary qudits and spin coherent states

Coupling spin ensembles via superconducting flux qubits

Robust quantum storage and retrieval in a hybrid system by controllable Stark-chirped rapid adiabatic passages

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