ScholarBank@NUShttps://scholarbank.nus.edu.sgThe DSpace digital repository system captures, stores, indexes, preserves, and distributes digital research material.Wed, 05 Aug 2020 11:40:23 GMT2020-08-05T11:40:23Z5061- Geometric phase induced by quantum nonlocalityhttps://scholarbank.nus.edu.sg/handle/10635/115124Title: Geometric phase induced by quantum nonlocality
Authors: Wang, Z.S.; Wu, C.; Feng, X.-L.; Kwek, L.C.; Lai, C.H.; Oh, C.H.; Vedral, V.
Abstract: By analyzing an instructive example, for testing many concepts and approaches in quantum mechanics, of a one-dimensional quantum problem with moving infinite square-well, we define geometric phase of the physical system. We find that there exist three dynamical phases from the energy, the momentum and local change in spatial boundary condition respectively, which is different from the conventional computation of geometric phase. The results show that the geometric phase can fully describe the nonlocal character of quantum behavior. © 2007 Elsevier B.V. All rights reserved.
Mon, 04 Feb 2008 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/1151242008-02-04T00:00:00Z
- Quantum tunneling via quantum geometric phasehttps://scholarbank.nus.edu.sg/handle/10635/97714Title: Quantum tunneling via quantum geometric phase
Authors: Wang, Z.S.; Kwek, L.C.; Lai, C.H.; Oh, C.H.
Abstract: A new geometric phase is proposed by considering both the energy and momentum conservation, where the corresponding dynamical phases have two parts differently from the conventional calculations for the phase. The results are applied to quantum tunneling process, which is helpful to distinguish the concept about the tunneling time. © 2006 Elsevier B.V. All rights reserved.
Mon, 11 Dec 2006 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/977142006-12-11T00:00:00Z
- Nonadiabatic geometric quantum computationhttps://scholarbank.nus.edu.sg/handle/10635/97328Title: Nonadiabatic geometric quantum computation
Authors: Wang, Z.S.; Wu, C.; Feng, X.-L.; Kwek, L.C.; Lai, C.H.; Oh, C.H.; Vedral, V.
Abstract: A different way to realize nonadiabatic geometric quantum computation is proposed by varying parameters in the Hamiltonian for nuclear-magnetic resonance, where the dynamical and geometric phases are implemented separately without the usual operational process. Therefore the phase accumulated in the geometric gate is a pure geometric phase for any input state. In comparison with the conventional geometric gates by rotating operations, our approach simplifies experimental implementations making them robust to certain experimental errors. In contrast to the unconventional geometric gates, our approach distinguishes the total and geometric phases and offers a wide choice of the relations between the dynamical and geometric phases. © 2007 The American Physical Society.
Fri, 05 Oct 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/973282007-10-05T00:00:00Z
- Dynamical symmetry and geometric phasehttps://scholarbank.nus.edu.sg/handle/10635/96276Title: Dynamical symmetry and geometric phase
Authors: Wang, Z.S.; Kwek, L.C.; Lai, C.H.; Oh, C.H.
Abstract: By considering dynamical symmetry between canonically equivalent systems, we investigate the connection between the geometric phase and dynamical invariants, where the Liouville-von-Neumann equation is directly deduced. Furthermore, we show that an arbitrary shift of the Hamiltonian, where f i(t) is a real function and Xi is a generator of dynamical symmetry, leaves the geometric phase invariant. © 2007 The Royal Swedish Academy of Sciences.
Sun, 01 Apr 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/962762007-04-01T00:00:00Z
- Scheme for unconventional geometric quantum computation in cavity QEDhttps://scholarbank.nus.edu.sg/handle/10635/97867Title: Scheme for unconventional geometric quantum computation in cavity QED
Authors: Feng, X.-L.; Wang, Z.; Wu, C.; Kwek, L.C.; Lai, C.H.; Oh, C.H.
Abstract: In this paper, we present a scheme for implementing the unconventional geometric two-qubit phase gate with nonzero dynamical phase based on two-channel Raman interaction of two atoms in a cavity. We show that the dynamical phase and the total phase for a cyclic evolution are proportional to the geometric phase in the same cyclic evolution; hence they possess the same geometric features as does the geometric phase. In our scheme, the atomic excited state is adiabatically eliminated, and the operation of the proposed logic gate involves only the metastable states of the atoms; thus the effect of the atomic spontaneous emission can be neglected. The influence of the cavity decay on our scheme is examined. It is found that the relations regarding the dynamical phase, the total phase, and the geometric phase in the ideal situation are still valid in the case of weak cavity decay. Feasibility and the effect of the phase fluctuations of the driving laser fields are also discussed. © 2007 The American Physical Society.
Wed, 09 May 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/978672007-05-09T00:00:00Z
- Unconventional geometric quantum computation in a two-mode cavityhttps://scholarbank.nus.edu.sg/handle/10635/53248Title: Unconventional geometric quantum computation in a two-mode cavity
Authors: Wu, C.; Wang, Z.; Feng, X.-L.; Goan, H.-S.; Kwek, L.C.; Lai, C.H.; Oh, C.H.
Abstract: We propose a scheme for implementing unconventional geometric quantum computation by using the interaction of two atoms with a two-mode cavity field. The evolution of the system results in a nontrivial two-qubit phase gate. The operation of the proposed gate involves only metastable states of the atom and hence is not affected by spontaneous emission. The effect of cavity decay on the gate is investigated. It is shown that the evolution time of the gate in the two-mode case is less than that in the single-mode case proposed by Feng [Phys. Rev. A 75, 052312 (2007)]. Thus the gate can be more decay tolerant than the previous one. The scheme can also be generalized to a system consisting of two atoms interacting with an N -mode cavity field. © 2007 The American Physical Society.
Thu, 09 Aug 2007 00:00:00 GMThttps://scholarbank.nus.edu.sg/handle/10635/532482007-08-09T00:00:00Z