On Nonuniqueness of Quantum Channel for Fixed Input-Output States: Case of Decoherence Channel
Open Access
- 22 January 2022
- Vol. 14 (2), 214
- https://doi.org/10.3390/sym14020214
Abstract
For a fixed pair of input and output states in the space of a system A, a quantum channel, i.e., a linear, completely positive and trace-preserving map, between them is not unique, in general. Here, this point is discussed specifically for a decoherence channel, which maps from a pure input state to a completely decoherent state like the thermal state. In particular, decoherence channels of two different types are analyzed: one is unital and the other is not, and both of them can be constructed through reduction of B in the total extended space , where is the space of an ancillary system B that is a replica of A. The nonuniqueness is seen to have its origin in the unitary symmetry in the extended space. It is shown in an example of a two-qubit system how such symmetry is broken in the objective subspace due to entanglement between A and B. A comment is made on possible relevance of the present work to nanothermodynamics in view of quantum Darwinism.
Keywords
Funding Information
- National Natural Science Foundation of China (11775084)
This publication has 20 references indexed in Scilit:
- Generic emergence of classical features in quantum DarwinismNature Communications, 2015
- The Big World of NanothermodynamicsEntropy, 2014
- Complementarity of quantum discord and classically accessible informationScientific Reports, 2013
- The thermostatistical aspect of Werner-type states and quantum entanglementJournal of Physics A: Mathematical and Theoretical, 2009
- Demonstration of two-qubit algorithms with a superconducting quantum processorNature, 2009
- Quantum DarwinismNature Physics, 2009
- Transforming quantum operations: Quantum supermapsEurophysics Letters, 2008
- THERMO FIELD DYNAMICSInternational Journal of Modern Physics B, 1996
- Thermal noise from pure-state quantum correlationsPhysical Review A, 1989
- On the interpretation of measurement in quantum theoryFoundations of Physics, 1970