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Laser Physics Letters

Tunnel-optical electron transitions in an asymmetric double quantum dot under correction field

Alexander V. Tsukanov, I. Yu. Kateev

Published Jun 27, 2025• 1 citation
Publisher

Abstract

Abstract Quantum operations on a charge qubit, which is represented by a single-electron double quantum dot (QD) with structure asymmetry, are considered. It is shown that with the help of an electric field created by voltage gates the tunnel coupling of the QD excited states is possible to control. An algorithm for performing single-qubit rotations based on a sequence of tunnel and optical transitions is described. The dependences of the correction electric field on geometric parameters of the gates are calculated.

DOI
10.1088/1612-202x/ade078

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Abstract Quantum operations on a charge qubit, which is represented by a single-electron double quantum dot (QD) with structure asymmetry, are considered. It is shown that with the help of an electric field created by voltage gates the tunnel coupling of the QD excited states is possible to control. An algorithm for performing single-qubit rotations based on a sequence of tunnel and optical transitions is described. The dependences of the correction electric field on geometric parameters of the gates are calculated.
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Abstract We studied the dynamics of a pair of single-electron double quantum dots (DQDs) under longitudinal and transverse static magnetic fields and time-dependent harmonic modulation of their interaction couplings. We propose to modulate the tunnel coupling between the QDs to produce one-qubit gates and the exchange coupling between DQDs to generate entangling gates, the set of operations required for quantum computing. We developed analytical approximations to set the conditions to control the qubits and applied them to numerical calculations to test the accuracy and robustness of the analytical model. The results shows that the unitary evolution of the two-electron state performs the designed operations even under conditions shifted from the ideal ones.
We propose a set of universal gate operations for the singlet-triplet qubit realized by two-electron spins in a double quantum dot, in the presence of a fixed inhomogeneous magnetic field. All gate operations are achieved by switching the potential offset between the two dots with an electrical bias, and do not require time-dependent control of the tunnel coupling between the dots. We analyze the two-electron dynamics and calculate the effective qubit rotation angle as a function of the applied electric bias. We present explicit gate sequences for single-qubit rotations about two orthogonal axes, and a CNOT gate sequence, completing the universal gate set.
PACS. 73.23.-b – Electronic transport in mesoscopic systems. Abstract. – We study entanglement of charge qubits in a vertical tunnel-coupled double quantum dot containing two interacting electrons. Exact diagonalization is used to compute the negativity characterizing entanglement. We find that entanglement can be efficiently generated and controlled by sidegate voltages, and describe how it can be detected. For large enough tunnel coupling, the negativity shows a pronounced maximum at an intermediate interaction strength within the Wigner molecule regime. Semiconductor few-electron quantum dots (QDs) continue to attract a lot of interest, as it has now become possible to experimentally control both the electronic spin and charge in a condensed-phase environment in an unprecedented manner. In particular, double quantum dots (DQDs) can be fabricated in a well-controlled fashion in high-quality semiconductor devices, and are currently under intense study [1–9]. Vertical or lateral tunnel-coupled DQDs are among the most promising candidates for realizing spin or charge qubits in a quantum information processor [10–12]. Their main advantages are scalability, good control of physical properties via tunable external (sidegate-) voltages or magnetic fields, and spatial separation
A single electron spin in a double quantum dot in a magnetic field is considered in terms of a four-level system. By describing the electron motion between the potential minima via spin-conserving tunneling and spin flip caused by a spin–orbit coupling, we inversely engineer faster-than-adiabatic state manipulation operations based on the geometry of four-dimensional rotations. In particular, we show how to transport a qubit among the quantum dots performing simultaneously required spin rotations.