High-fidelity spin entanglement using optimal control

Dolde, Florian; Bergholm, Ville; Wang, Ya; Jakobi, Ingmar; Naydenov, Boris; Pezzagna, Sébastien; Meijer, Jan; Jelezko, Fedor; Neumann, Philipp; Schulte‐Herbrüggen, Thomas; Biamonte, Jacob; Wrachtrup, Jörg

doi:10.1038/ncomms4371

Cited by 314 publications

(315 citation statements)

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“…However, the previously reported experiments, [17][18][19][20][21][22] utilise openloop optimisation techniques where the optimisation is performed before the actual experiment by separate computer simulations. The technique requires system-environment coupling information as detailed as possible to provide a robust solution.…”

Section: Introductionmentioning

confidence: 99%

“…Optimal control methods have been applied to several quantum information processing tasks with NV centres, [17][18][19][20][21][22] affirming their necessity and significance for quantum technology. However, the previously reported experiments, [17][18][19][20][21][22] utilise openloop optimisation techniques where the optimisation is performed before the actual experiment by separate computer simulations.…”

Section: Introductionmentioning

confidence: 99%

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Autonomous calibration of single spin qubit operations

et al. 2017

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Fully autonomous precise control of qubits is crucial for quantum information processing, quantum communication, and quantum sensing applications. It requires minimal human intervention on the ability to model, to predict, and to anticipate the quantum dynamics, as well as to precisely control and calibrate single qubit operations. Here, we demonstrate single qubit autonomous calibrations via closed-loop optimisations of electron spin quantum operations in diamond. The operations are examined by quantum state and process tomographic measurements at room temperature, and their performances against systematic errors are iteratively rectified by an optimal pulse engineering algorithm. We achieve an autonomous calibrated fidelity up to 1.00 on a time scale of minutes for a spin population inversion and up to 0.98 on a time scale of hours for a single qubit π 2 -rotation within the experimental error of 2%. These results manifest a full potential for versatile quantum technologies.npj Quantum Information (2017) 3:48 ; doi:10.1038/s41534-017-0049-8 INTRODUCTIONThe ability to precisely control and calibrate single qubit operations in solids is a key element for reliable and scalable high-performance quantum technologies, for instance quantumenhanced sensors and metrological devices. It is also the backbone of many quantum information processing tasks, which paves the way for the future realisation of quantum computation and communication. Together with efficient quantum system characterisations and dynamical predictions, 1,2 where human intervention is minimised, autonomous calibration of a single spin qubit is necessary for the realisation of such advanced quantum technologies. We report here experimental demonstrations of the autonomous calibration of a single spin qubit in diamond using closed-loop optimisation. Our spin qubit implementation is a single nitrogen-vacancy (NV) colour centre in diamond. It provides a suitable platform for a precise qubit manipulation to be realised. 3,4 Its remarkable features, such as optical initialisation and readout, and the ability to be manipulated by microwave fields at room temperature, make this physical system extremely attractive for many quantum technologies. 5 We have witnessed a vast array of demonstrations of the NV centres showing a great potential for future technologies, ranging from sub pico-Tesla magnetometry, 6 electric field and temperature sensing, 7,8 to probing molecular dynamics, 9 and single-cell magnetic imaging. 10 Furthermore, intertwinements between quantum information and metrology using NV centre-based systems yield novel and effective techniques towards the realisation of high-performance technologies, e.g. applying quantum error correction 11 and phase estimation 12 to improve magnetic field sensitivity. One way to reach such technology is to apply the closed-loop optimisation method for auto-calibrating the controls required to drive the system in the presence of experimental limitations and noise. Closed-loop optimal control has been already applied...

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Autonomous calibration of single spin qubit operations

et al. 2017

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“…A more general approach is provided by "optimal control," a well established procedure in which H C (t) is parameterized by a set of control variables, and a numerical search performed to optimize the fidelity with which the control objective is achieved [2]. The application of optimal control to quantum systems originated in NMR [1] and physical chemistry [2], and has expanded to include ultrafast physics [6], cold atoms [7,8], biomolecules [9], condensed matter spins [10], and superconducting circuits [11].…”

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confidence: 99%

Accurate and Robust Unitary Transformations of a High-Dimensional Quantum System

et al. 2015

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Quantum control in large dimensional Hilbert spaces is essential for realizing the power of quantum information processing. For closed quantum systems the relevant inputoutput maps are unitary transformations, and the fundamental challenge becomes how to implement these with high fidelity in the presence of experimental imperfections and decoherence. For two-level systems (qubits) most aspects of unitary control are well understood, but for systems with Hilbert space dimension d>2 (qudits), many questions remain regarding the optimal design of control Hamiltonians 1 and the feasibility of robust implementation 2,3 . Here we show that arbitrary, randomly chosen unitary transformations can be efficiently designed and implemented in a large dimensional Hilbert space (d=16) associated with the electronic ground state of atomic 133 Cs, 4 achieving fidelities above 0.98 as measured by randomized benchmarking 5 . Generalizing the concepts of inhomogeneous control 6 and dynamical decoupling 7 to d>2 systems, we further demonstrate that these qudit unitary maps can be made robust to both static and dynamic perturbations. Potential applications include improved fault-tolerance in universal quantum computation 8 , nonclassical state preparation for high-precision metrology 9 , implementation of quantum simulations 10 , and the study of fundamental physics related to open quantum systems and quantum chaos 11 .The goal of quantum control is to perform a desired transformation through dynamical evolution driven by a control Hamiltonian H C (t) . For example, one common objective is to evolve the system from a known initial state to a desired final state. If the control task is simple or special symmetries are present, it is sometimes possible to find a high-performing control Hamiltonian through intuition, or to construct one using group theoretic methods 12 . In this letter we explore the use of "optimal control" 1 to design control Hamiltonians for tasks of varying complexity, from state-to-state maps to unitary maps on the entire accessible Hilbert space. The basic procedure is well established: the Hamiltonian H C (t) is parameterized by a set of control variables, and a numerical search is performed to find values that optimize the fidelity with which the control objective is achieved. The application of optimal control to quantum systems originated in NMR 13 and physical chemistry 1 , and has since expanded to include, e. g., ultrafast physics 14 , cold atoms 15,16 , biological molecules 17 , spins in condensed matter 18 , and superconducting circuits 19 .We study the efficacy of numerical design and the performance of the resulting control Hamiltonians using a well developed testbed consisting of the electron and nuclear spins of individual 133 Cs atoms driven by radiofrequency (rf) and microwave (µw) magnetic fields (Fig. 1) 16 . Our experiments show that the optimal control strategy is adaptable to a wide range of control tasks, and that it can generate control Hamiltonians with excellent performance even in the prese...

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“…To this end there have been proposals to use solid-state emitters such as a periodically pumped quantum dot (QD) for the generation of a one-dimensional cluster states [4,5]. In this work we consider another possible solidstate system, the NV centers in diamond, to generate multi-photon entangled states.The NV center provides a hybrid spin system in which electron spins are used for fast [6], high-fidelity control [7] and readout [8,9], and nuclear spins are wellisolated from their environment yielding ultra-long coherence time [10]. Electron and nuclear spins could form a small-scale quantum register [11][12][13] allowing for e.g.…”

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confidence: 99%

“…The NV center provides a hybrid spin system in which electron spins are used for fast [6], high-fidelity control [7] and readout [8,9], and nuclear spins are wellisolated from their environment yielding ultra-long coherence time [10]. Electron and nuclear spins could form a small-scale quantum register [11][12][13] allowing for e.g.…”

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confidence: 99%

Generation of entangled photon strings using NV centers in diamond

2015

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We present a scheme to generate entangled photons using the NV centers in diamond. We show how the long-lived nuclear spin in diamond can mediate entanglement between multiple photons thereby increasing the length of entangled photon string. With the proposed scheme one could generate both n-photon GHZ and cluster states. We present an experimental scheme realizing the same and estimating the rate of entanglement generation both in the presence and absence of a cavity.With controlled generation and manipulation, quantum states of light are efficient carriers of quantum information with applications in quantum computing (QC), communications and cryptography. One of the major drawbacks with optical quantum information processing (QIP) is the absence of suitable nonlinear interactions to realize universal quantum gates, for example a CNOT gate between two photonic qubits. To overcome this difficulty one may choose the implementation of desired quantum computation through a one-way quantum computer model [1] which requires the initialization of the quantum register in a globally entangled cluster state. The computation is then followed by performing only single qubit measurements. The one-way quantum computer or the measurement-based quantum computation using photonic qubits (polarization states) has already been shown to be a fault-tolerant model for QC and is tolerant to qubit losses [2]. The main hurdle in realizing optical QIP using this scheme is the generation of multi-qubit cluster state, the key initialization step of the model. While the experimental implementations succeeded to generate 6-qubit photonic cluster state optically [3], scaling this number further is not so clear. To this end there have been proposals to use solid-state emitters such as a periodically pumped quantum dot (QD) for the generation of a one-dimensional cluster states [4,5]. In this work we consider another possible solidstate system, the NV centers in diamond, to generate multi-photon entangled states.The NV center provides a hybrid spin system in which electron spins are used for fast [6], high-fidelity control [7] and readout [8,9], and nuclear spins are wellisolated from their environment yielding ultra-long coherence time [10]. Electron and nuclear spins could form a small-scale quantum register [11][12][13] allowing for e.g. necessary high-fidelity quantum error correction [11]. Furthermore, the NV electron spin can be entangled with an emitted optical photon [14,15] and further quantum entanglement [16] and quantum teleportation [17] between two remote NV centers have already been experimentally demonstrated. We have also recently demonstrated the ability of this solid-state device to store quantum information from a light field into the defect spins and a repetitive readout of the memory, essential for scalable networks. In addition there have been other proposals to create large scalable QIP in diamond using a photonic architecture [18] where cluster/topological states of the long-lived nuclear spins in various defect center...

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High-fidelity spin entanglement using optimal control

Cited by 314 publications

References 58 publications

Autonomous calibration of single spin qubit operations

Autonomous calibration of single spin qubit operations

Accurate and Robust Unitary Transformations of a High-Dimensional Quantum System

Generation of entangled photon strings using NV centers in diamond

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