Driving at the Quantum Speed Limit: Optimal Control of a Two-Level System

Hegerfeldt, Gerhard C.

doi:10.1103/physrevlett.111.260501

Cited by 218 publications

(244 citation statements)

References 20 publications

Supporting

Mentioning

232

Contrasting

Unclassified

Order By: Relevance

“…We studied transfer times in the regime T/T π > 1 because the maximum speed of a quantum system evolution is bound in general by the quantum speed limit. 28,29 Numerical simulations support this fact when a rectangular microwave pulse shape is assumed (see Supplementary Material Section G). In part (b), we show our experimental results achieved via closed loop optimisation, which support these results for small detuning, when T/T π = 1.5.…”

Section: High Fidelity Population Inversion Via Closed-loop Controlmentioning

confidence: 61%

Autonomous calibration of single spin qubit operations

et al. 2017

View full text Add to dashboard Cite

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...

show abstract

Section: High Fidelity Population Inversion Via Closed-loop Controlmentioning

confidence: 61%

Autonomous calibration of single spin qubit operations

et al. 2017

View full text Add to dashboard Cite

show abstract

“…In the absence of direct driving of the qubit, Pontryagin's minimum principle proves that this bang-bang control achieves time optimality [15][16][17].…”

Section: A Indirect Control By a Quantum Actuatormentioning

confidence: 99%

Time-optimal control by a quantum actuator

Aiello

Cappellaro

2015

Phys. Rev. A

View full text Add to dashboard Cite

Indirect control of qubits by a quantum actuator has been proposed as an appealing strategy to manipulate qubits that couple only weakly to external fields. While universal quantum control can be easily achieved when the actuator-qubit coupling is anisotropic, the efficiency of this approach is less clear. Here we analyze the time efficiency of quantum actuator control. We describe a strategy to find time-optimal control sequences by the quantum actuator and compare their gate times with direct driving, identifying regimes where the actuator control performs faster. As a paradigmatic example, we focus on a specific implementation based on the nitrogen-vacancy center electronic spin in diamond (the actuator) and nearby 13 C nuclear spins (the qubits).

show abstract

“…The second scheme we consider is the CP protocol [25]. This scheme has been proved to be capable to control a system described by a LZ-type Hamiltonian at the maximum speed allowed by quantum mechanics [24,26]. In addition, the CP scheme corresponds to an analytical solution of the optimal control problem for these systems [26].…”

Section: B Efficiency and Speed Of Control Protocols For Csd Navigationmentioning

confidence: 99%

“…These various control strategies include the use of analytically wellestablished phenomena like the paradigmatic LandauZener (LZ) transition [12][13][14], Landau-Zener-Stückelberg interferometry [15,16], the composite pulse (CP) protocol and several other two-level control strategies [12,[24][25][26][27], and OCT [18][19][20][21][22][23]. For the experimental control strategies, as can be seen in [10,[15][16][17], the first stage is the measurement of the charge stability diagram (CSD).…”

Section: Introductionmentioning

confidence: 99%

Controlled high-fidelity navigation in the charge stability diagram of a double quantum dot

Coden¹,

Romero²,

Räsänen³

2015

J. Phys.: Condens. Matter

View full text Add to dashboard Cite

We propose an efficient control protocol for charge transfer in a double quantum dot. We consider numerically a two-dimensional model system, where the quantum dots are subjected to timedependent electric fields corresponding to experimental gate voltages. Our protocol enables navigation in the charge stability diagram from a state to another through controllable variation of the fields. We show that the well-known adiabatic Landau-Zener transition -when supplemented with a time-dependent field tailored with optimal control theory -can remarkably improve the transition speed. The results also lead to a simple control scheme that requires only a single parameter obtained from the experimental charge stability diagram. Eventually, we can control the system at the fastest speed allowed by the quantum dynamics and with a high fidelity.

show abstract

Driving at the Quantum Speed Limit: Optimal Control of a Two-Level System

Cited by 218 publications

References 20 publications

Autonomous calibration of single spin qubit operations

Autonomous calibration of single spin qubit operations

Time-optimal control by a quantum actuator

Controlled high-fidelity navigation in the charge stability diagram of a double quantum dot

Contact Info

Product

Resources

About