Robust Decoupling Techniques to Extend Quantum Coherence in Diamond

Ryan, Colm A.; Hodges, J. S.; Cory, David G.

doi:10.1103/physrevlett.105.200402

Cited by 340 publications

(402 citation statements)

References 26 publications

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“…2a, the feedback algorithm protects the qubit coherence against the noise created by the 13 C nuclear spin bath for times τ > 1 ms, much longer than the dephasing time. While the spin-bath in this experimental system is nonMarkovian and thus DD techniques have reached similar protection times [23], unlike DD this method would also be effective in the Markovian noise regime, with its ultimate limit set only by the coherence time of the ancillary spin and the qubit relaxation. These limits could be overcome by re-initialising the ancilla or, if additional ancillas (such as nearby 13 C spins) are available, by repeating the algorithm with fresh ancillas, or by concatenating layers of protections against multi-axis noise (see Methods).…”

Section: Figmentioning

confidence: 99%

Coherent feedback control of a single qubit in diamond

Hirose

Cappellaro

2016

Nature

103

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Engineering desired operations on qubits subjected to the deleterious effects of their environment is a critical task in quantum information processing, quantum simulation and sensing. The most common approach is to rely on open-loop quantum control techniques, including optimal control algorithms, based on analytical [1] or numerical [2] solutions, Lyapunov design [3] and Hamiltonian engineering [4]. An alternative strategy, inspired by the success of classical control, is feedback control [5]. Because of the complications introduced by quantum measurement [6], closed-loop control is less pervasive in the quantum settings and, with exceptions [7,8], its experimental implementations have been mainly limited to quantum optics experiments. Here we implement a feedback control algorithm with a solid-state spin qubit system associated with the Nitrogen Vacancy (NV) centre in diamond, using coherent feedback [9] to overcome limitations of measurement-based feedback, and show that it can protect the qubit against intrinsic dephasing noise for milliseconds. In coherent feedback, the quantum system is connected to an auxiliary quantum controller (ancilla) that acquires information about the system's output state (by an entangling operation) and performs an appropriate feedback action (by a conditional gate). In contrast to open-loop dynamical decoupling (DD) techniques [10], feedback control can protect the qubit even against Markovian noise and for an arbitrary period of time (limited only by the ancilla coherence time), while allowing gate operations. It is thus more closely related to Quantum Error Correction schemes [11][12][13][14], which however require larger and increasing qubit overheads. Increasing the number of fresh ancillas allows protection even beyond their coherence time. We can further evaluate the robustness of the feedback protocol, which could be applied to quantum computation and sensing, by exploring an interesting tradeoff between information gain and decoherence protection, as measurement of the ancilla-qubit correlation after the feedback algorithm voids the protection, even if the rest of the dynamics is unchanged.To demonstrate coherent feedback with spin qubits, we choose two of the most common tasks for qubits, implementing the no-operation (NOOP) and NOT gates, while cancelling the effects of noise. A simple, measurementbased feedback scheme, exploiting one ancillary qubit, was proposed in [16]. The correction protocol (Fig. 1a) works by entangling the qubit-ancilla system before the desired gate operation. By selecting an entangling operation U c appropriate for the type of bath acting on the system, information about the noise action is encoded in the ancilla state. After undoing the entangling operation, the qubit coherence can be restored by a feedback action, Hadamard gates prepare and read out a superposition state of the qubit, |φ q = 1 √ 2 (|0 + |1 ). Amid entangling gates between qubit and ancilla, the qubit is subjected to noise (and possibly unitary gates U ). We assume the ancil...

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Section: Figmentioning

confidence: 99%

Coherent feedback control of a single qubit in diamond

Hirose

Cappellaro

2016

Nature

103

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“…In particular, dynamical decoupling techniques pioneered in nuclear magnetic resonance have recently been applied successfully to extend the effective T 2 of single NV-diamond electronic spins by more than an order of magnitude [18][19][20] .…”

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confidence: 99%

Suppression of spin-bath dynamics for improved coherence of multi-spin-qubit systems

et al. 2012

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multi-qubit systems are crucial for the advancement and application of quantum science. such systems require maintaining long coherence times while increasing the number of qubits available for coherent manipulation. For solid-state spin systems, qubit coherence is closely related to fundamental questions of many-body spin dynamics. Here we apply a coherent spectroscopic technique to characterize the dynamics of the composite solid-state spin environment of nitrogen-vacancy colour centres in room temperature diamond. We identify a possible new mechanism in diamond for suppression of electronic spin-bath dynamics in the presence of a nuclear spin bath of sufficient concentration. This suppression enhances the efficacy of dynamical decoupling techniques, resulting in increased coherence times for multispin-qubit systems, thus paving the way for applications in quantum information, sensing and metrology.

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“…In order to decouple the NV spin from the decohering environment, many pulse-based dynamical decoupling protocols have been investigated and proven efficient. 25,[39][40][41][42][43][44][45][46] At the same time, an alternative approach based on the continuous dynamical decoupling has been extensively investigated. 11,[47][48][49][50][51][52][53][54][55][56][57][58] Within this approach, strong resonant driving is applied to the NV center.…”

Section: Introductionmentioning

confidence: 99%

Decay of the rotary echoes for the spin of a nitrogen-vacancy center in diamond

Mkhitaryan

Dobrovitski

2014

Phys. Rev. B

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We study dynamics of the electron spin of a nitrogen-vacancy (NV) center subjected to a strong driving field with periodically reversed direction (train of rotary echoes). We use analytical and numerical tools to analyze in detail the form and timescales of decay of the rotary echo train, modeling the decohering spin environment as a random magnetic field. We demonstrate that the problem can be exactly mapped onto a model of spin 1 coupled to a single bosonic mode with imaginary frequency. This mapping allows comprehensive analytical investigation beyond the standard BlochRedfield-type approaches. We explore the decay of the rotary echo train under assumption of strong driving, and identify the most important regimes of the decay. The analytical results are compared with the direct numerical simulations to confirm quantitative accuracy of our study. We present the results for realistic environment of substitutional nitrogen atoms (P1 centers), and provide a simplified but accurate description for decay of the rotary echo train of the NV center's spin. The approach presented here can also be used to study decoherence and longitudinal relaxation of other spin systems under conditions of strong driving.

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Robust Decoupling Techniques to Extend Quantum Coherence in Diamond

Cited by 340 publications

References 26 publications

Coherent feedback control of a single qubit in diamond

Coherent feedback control of a single qubit in diamond

Suppression of spin-bath dynamics for improved coherence of multi-spin-qubit systems

Decay of the rotary echoes for the spin of a nitrogen-vacancy center in diamond

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