scholarly journals Active Stabilization, Quantum Computation, and Quantum State Synthesis

1997 ◽  
Vol 78 (11) ◽  
pp. 2252-2255 ◽  
Author(s):  
A. M. Steane
Keyword(s):  
Quantum Computation ◽  
Quantum State ◽  
Active Stabilization

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 Effective Number Theory: Counting the Identities of a Quantum State

Entropy ◽  
2020 ◽  
Vol 22 (11) ◽  
pp. 1273
Author(s):  
Ivan Horváth ◽  
Robert Mendris
Keyword(s):  
Number Theory ◽  
Quantum Mechanics ◽  
Quantum Computation ◽  
Quantum State ◽  
Quantum Dynamics ◽  
Quantum Physics ◽  
Quantum Algorithm ◽  
Effective Number ◽  
Additive Theory ◽  
Participation Number

Quantum physics frequently involves a need to count the states, subspaces, measurement outcomes, and other elements of quantum dynamics. However, with quantum mechanics assigning probabilities to such objects, it is often desirable to work with the notion of a “total” that takes into account their varied relevance. For example, such an effective count of position states available to a lattice electron could characterize its localization properties. Similarly, the effective total of outcomes in the measurement step of a quantum computation relates to the efficiency of the quantum algorithm. Despite a broad need for effective counting, a well-founded prescription has not been formulated. Instead, the assignments that do not respect the measure-like nature of the concept, such as versions of the participation number or exponentiated entropies, are used in some areas. Here, we develop the additive theory of effective number functions (ENFs), namely functions assigning consistent totals to collections of objects endowed with probability weights. Our analysis reveals the existence of a minimal total, realized by the unique ENF, which leads to effective counting with absolute meaning. Touching upon the nature of the measure, our results may find applications not only in quantum physics, but also in other quantitative sciences.

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 QUANTUM KOLMOGOROV COMPLEXITY AND ITS APPLICATIONS

2007 ◽  
Vol 05 (05) ◽  
pp. 729-750 ◽  
Author(s):  
CATERINA E. MORA ◽  
HANS J. BRIEGEL ◽  
BARBARA KRAUS
Keyword(s):  
Quantum Computation ◽  
Quantum State ◽  
Kolmogorov Complexity ◽  
Communication Complexity ◽  
Quantum States ◽  
Qubit State ◽  
Binary String ◽  
Classical Communication ◽  
Pure Quantum State ◽  
Definition Of

Kolmogorov complexity is a measure of the information contained in a binary string. We investigate here the notion of quantum Kolmogorov complexity, a measure of the information required to describe a quantum state. We show that for any definition of quantum Kolmogorov complexity measuring the number of classical bits required to describe a pure quantum state, there exists a pure n-qubit state which requires exponentially many bits of description. This is shown by relating the classical communication complexity to the quantum Kolmogorov complexity. Furthermore, we give some examples of how quantum Kolmogorov complexity can be applied to prove results in different fields, such as quantum computation and thermodynamics, and we generalize it to the case of mixed quantum states.

scholarly journals Quantum computation and quantum-state engineering driven by dissipation

2009 ◽  
Vol 5 (9) ◽  
pp. 633-636 ◽  
Author(s):  
Frank Verstraete ◽  
Michael M. Wolf ◽  
J. Ignacio Cirac
Keyword(s):  
Quantum Computation ◽  
Quantum State ◽  
Quantum State Engineering

scholarly journals Characterizing measurement-based quantum gates in quantum many-body systems using correlation functionsThis paper was presented at the Theory CANADA 4 conference, held at Centre de recherches mathématiques, Montréal, Québec, Canada on 4–7 June 2008.

2009 ◽  
Vol 87 (3) ◽  
pp. 219-224 ◽  
Author(s):  
Thomas Chung ◽  
Stephen D. Bartlett ◽  
Andrew C. Doherty
Keyword(s):  
Quantum Computation ◽  
Quantum State ◽  
Correlation Functions ◽  
Quantum Gates ◽  
Many Body ◽  
Adaptive Measurements ◽  
Many Body Systems ◽  
Resource State

In measurement-based quantum computation (MBQC), local adaptive measurements are performed on the quantum state of a lattice of qubits. Quantum gates are associated with a particular measurement sequence, and one way of viewing MBQC is that such a measurement sequence prepares a resource state suitable for “gate teleportation”. We demonstrate how to quantify the performance of quantum gates in MBQC by using correlation functions on the pre-measurement resource state.

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