Coherent control and charge echo in a GaAs charge qubit

Abstract

In fulfilling the non-adiabatic requirement of pulse sequences, it is challenging to perform multi-pulse quantum control of a charge qubit. By optimizing our charge qubit and pulse parameters, we experimentally demonstrate the coherent control and echo process of a GaAs charge qubit. We firstly employed a single non-adiabatic voltage pulse to perform the Larmor oscillation experiment and determine the optimal operation pulses. Then, we produced Ramsey fringes using two pulses and extracted the decoherence time from the Ramsey fringes. More importantly, we successfully applied a charge echo pulse sequence to increase the extracted inhomogeneous dephasing time to ∼1360 ps. Our results show that the low-frequency noise is the important dephasing limiter of the coherence time of the charge qubit in the GaAs system.

Tunable charge qubit based on barrier-controlled triple quantum dots

“…The gate operations can be performed when ∆ξ is tuned to 0 meV and 0.504 meV respectively while maintaining ξ 1 + ξ 2 = 3.5 meV. Our simulation results are consistent with the typical oscillation frequency observed in charge qubit schemes where Rabi oscillation frequency ranges from ∼ 1 GHz to ∼ 5 GHz [12,13,37,66,67]. In addition, our proposed qubit scheme allows additional controllability of the oscillation frequency which is absent in the conventional charge qubit.…”

“…Perhaps the most intuitive realization is the double-quantum-dot charge qubit, for which an electron is allowed to occupy either one dot or the other, serving as the two logical states. Universal single-qubit operation can be performed by alternating between zero and large detuning ("tilt control") [1,[7][8][9][10][11][12], which achieves x and z-axis rotations, respectively. While this charge qubit has been demonstrated early-on to have very fast gate operations [1,13], it at the same time strongly suffers from charge noises [12,14,15], which has limited its development.…”

“…Universal single-qubit operation can be performed by alternating between zero and large detuning ("tilt control") [1,[7][8][9][10][11][12], which achieves x and z-axis rotations, respectively. While this charge qubit has been demonstrated early-on to have very fast gate operations [1,13], it at the same time strongly suffers from charge noises [12,14,15], which has limited its development. Spin qubits, on the other hand, are much less sensitive to charge noises [16].…”

All-Microwave Control and Dispersive Readout of Gate-Defined Quantum Dot Qubits in Circuit Quantum Electrodynamics

“…In a more conventional approach, in which DQD charge qubits are manipulated using non-adiabatic pulses and read out by capacitively coupled charge detectors, T 2 coherence times of up to (7 ± 2.5) ns in GaAs [8] and (2.1 ± 0.4) ns in Si [16] have been observed. Spin Echo experiments performed with non-adiabatic pulses [17] found echo times of T 2,echo ∼ (1.4 ± 0.4) ns in GaAs [18] and Si [16]. Recently, first microwave driven coherent operations showed improved qubit control and a T 2,echo ∼ (2.2 ± 0.1) ns in three electron DQDs in SiGe [19], which is operated as hybrid spin and charge qubit.…”

Suppression of Leakage for a Charge Qubit in Triangular Triple Quantum Dots

“…Universal singlequbit operations of the charge qubit can be achieved by alternating the relative energy between the two dots [2,3], and two-qubit gates can be performed using the electrostatic coupling between them [4][5][6]. While this charge qubit can have very fast gate operations, it at the same time suffers heavily from charge noises, leading to very short coherence times [7][8][9][10][11][12]. Various proposals have been put forward to improve the control of charge qubits for quantum information processing, including ultrafast gates [13], ac control around certain sweet spots [14], or hybrid qubits that combine advantages of manipulating charge and spin states [15][16][17][18][19].…”