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YiJing Yan

Publications and source records attributed to YiJing Yan.

121 records · Page 7Linked to original sources
arXiv2005

Quantum master equation approach to quantum transport through mesoscopic systems

For quantum transport through mesoscopic system, a quantum master equation approach is developed in terms of compact expressions for the transport current and the reduced density matrix of the system. The present work is an extension of Gurvitz's approach for quantum transport and quantum measurement, namely, to finite temperature and arbitrary bias voltage. Our derivation starts from a second-order cummulant expansion of the tunneling Hamiltonian, then follows conditional average over the electrode reservoir states. As a consequence, in the usual weak tunneling regime, the established formalism is applicable for a wide range of transport problems. The validity of the formalism and its convenience in application are well illustrated by a number of examples.

cond-mat.mes-hall↗
arXiv2004

Spontaneous Relaxation of a Charge Qubit under Electrical Measurement

In this work we first derive a generalized conditional master equation for quantum measurement by a mesoscopic detector, then study the readout characteristics of qubit measurement where a number of new features are found. The work would in particular highlight the qubit spontaneous relaxation effect induced by the measurement itself rather than an external thermal bath.

quant-ph↗
arXiv2004

Exact quantum master equation via the calculus on path integrals

An exact quantum master equation formalism is constructed for the efficient evaluation of quantum non-Markovian dissipation beyond the weak system-bath interaction regime in the presence of time-dependent external field. A novel truncation scheme is further proposed and compared with other approaches to close the resulting hierarchically coupled equations of motion. The interplay between system-bath interaction strength, non-Markovian property, and required level of hierarchy is also demonstrated with the aid of simple spin-boson systems.

quant-ph↗
arXiv2003

Quantum measurement of a solid-state qubit: A unified quantum master equation approach revisited

Quantum measurement of a solid-state qubit by a mesoscopic detector is of fundamental interest in quantum physics and an essential issue in quantum computing. In this work, by employing a unified quantum master equation approach constructed in our recent publications, we study the measurement-induced relaxation and dephasing of the coupled-quantum-dot states measured by a quantum-point-contact. Our treatment pays particular attention on the detailed-balance relation, which is a consequence of properly accounting for the energy exchange between the qubit and detector during the measurement process. As a result, our theory is applicable to measurement at arbitrary voltage and temperature. Both numerical and analytical results for the qubit relaxation and dephasing are carried out, and new features are highlighted in concern with their possible relevance to future experiments.

cond-mat.mes-hall↗
arXiv2003

Non-adiabatic geometric quantum computation with trapped ions

We propose a non-adiabatic scheme for geometric quantum computation with trapped ions. By making use of the Aharonov-Anandan phase, the proposed scheme not only preserves the globally geometric nature in quantum computation, but also provides the advantage of non-adiabaticity that overcomes the problem of slow evolution in the existing adiabatic schemes. Moreover, the present scheme requires only two atomic levels in each ion, making it an appealing candidate for quantum computation.

quant-ph↗
arXiv2002

Characterization of entanglement transformation via group representation theory

Entanglement transformation of composite quantum systems is investigated in the context of group representation theory. Representation of the direct product group $SL(2,C)\otimes SL(2,C)$, composed of local operators acting on the binary composite system, is realized in the four-dimensional complex space in terms of a set of novel bases that are pseudo orthonormalized. The two-to-one homomorphism is then established for the group $SL(2,C)\otimes SL(2,C)$ onto the $SO(4,C)$. It is shown that the resulting representation theory leads to the complete characterization for the entanglement transformation of the binary composite system.

quant-ph↗
arXiv2002

Ultrafast geometric manipulation of electron spin and detection of the geometric phase via Faraday rotation spectroscopy

Time-resolved Faraday rotation spectroscopy is currently exploited as a powerful technique to probe spin dynamics in semiconductors. We propose here an all-optical approach to geometrically manipulate electron spin and to detect the geometric phase by this type of extremely sensitive experiment. The global nature of the geometric phase can make the quantum manipulation more stable, which may find interesting application in quantum devices.

quant-ph↗
arXiv2002

Evaluating holonomic quantum computation: beyond adiabatic limitation

The proposal of the optical scheme for holonomic quantum computation is evaluated based on dynamical resolution to the system beyond adiabatic limitation. The time-dependent Schrödinger equation is exactly solved by virtue of the cranking representation and gauge transformation approach. Besides providing rigorous confirmation to holonomies of the geometrical prediction that holds for the ideally adiabatic situation, the dynamical resolution enables one to evaluate elaborately the amplitude of the nonadiabatic deviation, so that the errors induced to the quantum computation can be explicitly estimated.

quant-ph↗
arXiv2002

High coherent solid-state qubit from a pair of quantum dots

In this letter we propose a scheme to build up high coherent solid-state quantum bit (qubit) from two coupled quantum dots. Quantum information is stored in electron-hole pair state with the electron and hole locating in different dots, and universal quantum gates involving any pair of qubits are realized by effective coupling interaction via virtually exchanging cavity photons.

quant-ph↗
arXiv2002

Quantum computation with coupled-quantum-dots embedded in optical microcavities

Based on an idea that spatial separation of charge states can enhance quantum coherence, we propose a scheme for quantum computation with quantum bit (qubit) constructed from two coupled quantum dots. Quantum information is stored in electron-hole pair state with the electron and hole locating in different dots, which enables the qubit state being very long-lived. Universal quantum gates involving any pair of qubits are realized by coupling the quantum dots through cavity photon which is a hopeful candidate to transfer long-range information. Operation analysis is carried out by estimating the gate time versus the decoherence time.

quant-ph↗
arXiv2001

Electrical transport through individual DNA molecules

A theoretical study is presented to quantitatively analyze the transport experiment through individual DNA molecules reported recently by Porath {\it et al.} [Nature {\bf 403}, 635 (2000)]. A variety of valuable quantities are identified by contacting the theoretical model with the measured data. The partially decoherent nature on the GC pairs of DNA is elaborated in contrast to the completely incoherent hopping mechanism discussed in the context of charge transfer experiments.

cond-mat.mes-hall↗
arXiv2001

Tunneling in partial coherence through a series of barriers: an explicit result from a pure dephasing model

Within the Büttiker dephasing model, the backscattering in the dephasing process is eliminated by setting a proper boundary condition. Explicit expression is carried out for the effective total tunneling probability in the presence of multiple pure dephasing scatterers with partial coherence. The derived formula is illustrated analytically by various limiting cases, and numerically for its application in tunneling through multi-barrier systems.

cond-mat.mes-hall↗