scholarly journals Blind Witnesses Quench Quantum Interference without Transfer of Which-Path Information

Entropy ◽  
2020 ◽  
Vol 22 (7) ◽  
pp. 776
Author(s):  
Craig S. Lent
Keyword(s):  
Magnetic Flux ◽  
Quantum Computation ◽  
Time Evolution ◽  
Quantum State ◽  
Quantum Interference ◽  
Quantum Double ◽  
Global System ◽  
Path Information ◽  
Interference Oscillations ◽  
Loss Of Coherence

Quantum computation is often limited by environmentally-induced decoherence. We examine the loss of coherence for a two-branch quantum interference device in the presence of multiple witnesses, representing an idealized environment. Interference oscillations are visible in the output as the magnetic flux through the branches is varied. Quantum double-dot witnesses are field-coupled and symmetrically attached to each branch. The global system—device and witnesses—undergoes unitary time evolution with no increase in entropy. Witness states entangle with the device state, but for these blind witnesses, which-path information is not able to be transferred to the quantum state of witnesses—they cannot “see” or make a record of which branch is traversed. The system which-path information leaves no imprint on the environment. Yet, the presence of a multiplicity of witnesses rapidly quenches quantum interference.

scholarly journals Adjustable Quantum Interference Oscillations in Sb-Doped Bi2Se3 Topological Insulator Nanoribbons

ACS Nano ◽  
2020 ◽  
Vol 14 (10) ◽  
pp. 14118-14125
Author(s):  
Hong-Seok Kim ◽  
Tae-Ha Hwang ◽  
Nam-Hee Kim ◽  
Yasen Hou ◽  
Dong Yu ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Quantum Interference ◽  
Interference Oscillations

EFFICIENT ALGORITHM FOR INITIALIZING AMPLITUDE DISTRIBUTION OF A QUANTUM REGISTER

2001 ◽  
Vol 15 (27) ◽  
pp. 1259-1264 ◽  
Author(s):  
M. ANDRECUT ◽  
M. K. ALI
Keyword(s):  
Information Processing ◽  
Quantum Information ◽  
Quantum Computation ◽  
Quantum State ◽  
Efficient Algorithm ◽  
Quantum Information Processing ◽  
Amplitude Distribution ◽  
Quantum Register

The preparation of a quantum register in an arbitrary superposed quantum state is an important operation for quantum computation and quantum information processing. Here, we present an efficient algorithm which requires a polynomial number of elementary operations for initializing the amplitude distribution of a quantum register.

scholarly journals Silicon-based spin and charge quantum computation

2005 ◽  
Vol 77 (2) ◽  
pp. 201-222 ◽  
Author(s):  
Belita Koiller ◽  
Xuedong Hu ◽  
Rodrigo B. Capaz ◽  
Adriano S. Martins ◽  
Sankar Das Sarma
Keyword(s):  
Quantum Computation ◽  
Quantum Interference ◽  
Quantum Computer ◽  
Building Blocks ◽  
Shallow Donor ◽  
Molecular Ions ◽  
Conduction Band Edge ◽  
Tunnel Coupling ◽  
Qubit Operations ◽  
Silicon Based

Silicon-based quantum-computer architectures have attracted attention because of their promise for scalability and their potential for synergetically utilizing the available resources associated with the existing Si technology infrastructure. Electronic and nuclear spins of shallow donors (e.g. phosphorus) in Si are ideal candidates for qubits in such proposals due to the relatively long spin coherence times. For these spin qubits, donor electron charge manipulation by external gates is a key ingredient for control and read-out of single-qubit operations, while shallow donor exchange gates are frequently invoked to perform two-qubit operations. More recently, charge qubits based on tunnel coupling in P+2 substitutional molecular ions in Si have also been proposed. We discuss the feasibility of the building blocks involved in shallow donor quantum computation in silicon, taking into account the peculiarities of silicon electronic structure, in particular the six degenerate states at the conduction band edge. We show that quantum interference among these states does not significantly affect operations involving a single donor, but leads to fast oscillations in electron exchange coupling and on tunnel-coupling strength when the donor pair relative position is changed on a lattice-parameter scale. These studies illustrate the considerable potential as well as the tremendous challenges posed by donor spin and charge as candidates for qubits in silicon.

HIGH FREQUENCY AHARONOV–BOHM OSCILLATIONS IN CARBON NANOTUBES

2003 ◽  
Vol 17 (04) ◽  
pp. 159-165
Author(s):  
LINFENG YANG ◽  
JIE JIANG ◽  
JINMING DONG
Keyword(s):  
Carbon Nanotubes ◽  
Magnetic Flux ◽  
High Frequency ◽  
Quantum Interference ◽  
Weak Localization ◽  
Experimental Results ◽  
Single Wall Carbon Nanotubes ◽  
Multiple Cycle ◽  
Breaking Length ◽  
Aharonov Bohm

We give a multiple-cycle quantum interference model and obtain magnetoresistance (MR) expression in the framework of the weak localization. The MR expression based upon finite phase-breaking length Lφ can explain well several experimental results about distinct negative magnetoresistance of carbon nanotubes. The higher-order oscillation peaks with magnetic flux exist in the MR can also be explained by our model. And a new method to measure the phase-breaking length Lφ of the single-wall carbon nanotubes has been proposed.

COLLAPSE AND REVIVAL EFFECT IN A MESOSCOPIC LC CIRCUIT

2004 ◽  
Vol 18 (08) ◽  
pp. 1217-1224 ◽  
Author(s):  
HAI-MEI LUO ◽  
YING-HUA JI ◽  
JIE LIU
Keyword(s):  
Time Evolution ◽  
Dynamic Behavior ◽  
Quantum State ◽  
Tunnel Junction ◽  
Coherent States ◽  
The State ◽  
Quantum States ◽  
Quantum Superposition ◽  
Coupling Energy ◽  
Lc Circuit

This paper studied the time evolution of quantum state in a mesoscopic LC circuit with the coupling energy caused by mesoscopic capacitor acting as a tunnel junction. It indicates that the state of the junction evolves into the quantum superposition of two coherent states and, in the state, nonclassical squeezing properties of the circuit appear. It also indicates that the dynamic behavior of the current shows collapse and revival phenomenon. The research in the paper will be helpful to miniaturize integrate circuits and electric components. It will be also important for the utilization of mesoscopic circuits to evolve the quantum states, which work as information carriers.

QUANTUM WAVEGUIDE THEORY FOR TRIPLY CONNECTED AHARONOV–BOHM RINGS

1996 ◽  
Vol 10 (06) ◽  
pp. 701-712 ◽  
Author(s):  
CHANG-MO RYU ◽  
SAM YOUNG CHO ◽  
MINCHEOL SHIN ◽  
KYOUNG WAN PARK ◽  
SEONGJAE LEE ◽  
...  
Keyword(s):  
Magnetic Flux ◽  
Wave Vector ◽  
Quantum Interference ◽  
Transmission Probability ◽  
Interference Effects ◽  
Quantum Waveguide ◽  
One Dimensional ◽  
Waveguide Theory ◽  
Aharonov Bohm ◽  
Transmission And Reflection

Quantum interference effects for a mesoscopic loop with three leads are investigated by using a one-dimensional quantum waveguide theory. The transmission and reflection probabilities are analytically obtained in terms of the magnetic flux, arm length, and wave vector. Oscillation of the magnetoconductance is explicitly demonstrated. Magnetoconductance is found to be sharply peaked for certain localized values of flux and kl. In addition, it is noticed that the periodicity of the transmission probability with respect to kl depends more sensitively on the lead position, compared to the case of the two-lead loop.

scholarly journals Entanglement and adiabatic quantum computation

2006 ◽  
Vol 84 (6-7) ◽  
pp. 645-651 ◽  
Author(s):  
D Ahrensmeier
Keyword(s):  
Quantum Computation ◽  
Time Evolution ◽  
Search Algorithm ◽  
Time Dependent ◽  
Quantum Search ◽  
Quantum Search Algorithm ◽  
Adiabatic Quantum Computation ◽  
Alternative Approach ◽  
03.67 Mn

Adiabatic quantum computation provides an alternative approach to quantum computation using a time-dependent Hamiltonian. The time evolution of entanglement during the adiabatic quantum search algorithm is studied, and its relevance as a resource is discussed.PACS Nos.: 03.67.–a, 03.67.Lx, 03.67.Mn

scholarly journals The Density Matrix via Few Dominant Observables: The Quantum Interference in the Isotope Effect for Atto-Pumped N2

2021 ◽  
Author(s):  
Ksenia Komarova ◽  
Francoise Remacle ◽  
Raphael D. Levine
Keyword(s):  
Density Matrix ◽  
Time Evolution ◽  
Isotope Effect ◽  
Lagrange Multipliers ◽  
Quantum Interference ◽  
Electronic States ◽  
Compact Representation ◽  
Nuclear Dynamics ◽  
Analytical Results

In our paper a compact representation of the density as a function of a few observables is examined for the coupled electron-nuclear dynamics unfolding on three electronic states. The time-evolution of the density, populations and coherences, is accurately captured by the time-evolution of only nine coefficients, the Lagrange multipliers of these observables. We use a specific example of the isotope effect in atto-pumped N<sub>2</sub> to show that both classical and quantal effects of mass are well reproduced by this compact description. Simple analytical results for the surprisal are given, which allows a factorization of these two effects.

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