Subgap dynamics of double quantum dot coupled between superconducting and normal leads

AbstractDynamical processes induced by the external time-dependent fields can provide valuable insight into the characteristic energy scales of a given physical system. We investigate them here in a nanoscopic heterostructure, consisting of the double quantum dot coupled in series to the superconducting and the metallic reservoirs, analyzing its response to (i) abrupt bias voltage applied across the junction, (ii) sudden change of the energy levels, and imposed by (iii) their periodic driving. We explore subgap properties of this setup which are strictly related to the in-gap quasiparticles and discuss their signatures manifested in the time-dependent charge currents. The characteristic multi-mode oscillations, their beating patters and photon-assisted harmonics reveal a rich spectrum of dynamical features that might be important for designing the superconducting qubits.

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Subgap Dynamics of Double Quantum Dot Coupled Between Superconducting and Normal Leads

10.21203/rs.3.rs-223103/v1 ◽

2021 ◽

Author(s):

Bartłomiej Baran ◽

Ryszard Taranko ◽

Tadeusz Domański

Keyword(s):

Quantum Dot ◽

Energy Levels ◽

Sudden Change ◽

Time Dependent ◽

Double Quantum ◽

Valuable Insight ◽

Characteristic Energy ◽

Double Quantum Dot ◽

In Series ◽

External Time

Abstract Dynamical processes induced by the external time-dependent fields can provide valuable insight into the characteristic energy scales of a given physical system. We investigate them here in a nanoscopic heterostructure, consisting of the double quantum dot coupled in series to the superconducting and the metallic reservoirs, analyzing its response to (i) abrupt bias voltage applied across the junction, (ii) sudden change of the energy levels, and imposed by (iii) their periodic driving. We explore subgap properties of this setup which are strictly related to the in-gap quasiparticles and discuss their signatures manifested in the time-dependent charge currents. The characteristic multi-mode oscillations, their beating patters and photon-assisted harmonics reveal a rich spectrum of dynamical features that might be important for designing the superconducting qubits.

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Investigation of silicon isolated double quantum-dot energy levels for quantum computation

Microelectronic Engineering ◽

10.1016/j.mee.2006.01.174 ◽

2006 ◽

Vol 83 (4-9) ◽

pp. 1818-1822 ◽

Cited By ~ 7

Author(s):

Michael G. Tanner ◽

David G. Hasko ◽

David A. Williams

Keyword(s):

Quantum Dot ◽

Quantum Computation ◽

Energy Levels ◽

Double Quantum ◽

Double Quantum Dot

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Electronic Transport Through Double Quantum Dot Coupled to Majorana Bound States and Ferromagnetic Leads

Frontiers in Physics ◽

10.3389/fphy.2020.616107 ◽

2021 ◽

Vol 8 ◽

Author(s):

Li-Wen Tang ◽

Wei-Guo Mao

Keyword(s):

Quantum Dot ◽

Coupling Strength ◽

Bound States ◽

High Efficiency ◽

Energy Levels ◽

Electrical Current ◽

Function Technique ◽

Double Quantum ◽

Majorana Bound States ◽

Double Quantum Dot

We have studied theoretically the properties of electrical current and tunnel magnetoresistance (TMR) through a serially connected double quantum dot (DQD) sandwiched between two ferromagnetic leads by using the nonequilibrium Green’s function technique. We consider that each of the DQD couples to one mode of the Majorana bound states (MBSs) formed at the ends of a topological superconductor nanowire with spin-dependent coupling strength. By adjusting the sign of the spin polarization of dot–MBS coupling strength and the arrangement of magnetic moments of the two leads, the currents’ magnitude can be effectively enhanced or suppressed. Under some conditions, a negative TMR emerges which is useful in detection of the MBSs, a research subject currently under extensive investigations. Moreover, the amplitude of the TMR can be adjusted in a large regime by variation of several system parameters, such as direct hybridization strength between the MBSs or the dots and the positions of the dots’ energy levels. Such tunable currents and TMR may also find use in high-efficiency spintronic devices or information processes.

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Entanglement of two-electron spin states in a double quantum dot

International Journal of Quantum Information ◽

10.1142/s021974991750006x ◽

2017 ◽

Vol 15 (01) ◽

pp. 1750006 ◽

Cited By ~ 2

Author(s):

V. G. Bagrov ◽

D. M. Gitman ◽

A. D. Levin ◽

M. S. Meireles

Keyword(s):

Magnetic Field ◽

Quantum Dot ◽

Electron Spin ◽

Coherent Control ◽

Spin Exchange ◽

Time Dependent ◽

Double Quantum ◽

Spin States ◽

Quantum Bit ◽

Double Quantum Dot

Recently, an implementation of a universal set of one- and two-quantum-bit gates for quantum computation using spin states of coupled single-electron quantum dots was proposed. It was demonstrated that it is possible to execute a coherent control of a quantum system based on two-electron spin states in a double quantum dot, allowing state preparation, coherent manipulation, and projective readout. This possibility is based on rapid electrical control of the spin exchange interaction. These results motivated us to develop a formal theoretical study of the corresponding model of two coupled spins placed in a magnetic field and subjected to a time-dependent mutual Heisenberg interaction. Using possible exact solutions of the corresponding quantum problem, we study entangling of different separable initial states in this model. It is demonstrated that the entanglement due to a time-dependent Heisenberg interaction is dominating in comparison with the entanglement due to the action of an external magnetic field.

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