Quantum Systems, Information and Control
http://hdl.handle.net/2160/2972
2018-04-23T03:59:17ZQuantum filtering for systems driven by fields in single-photon states or superposition of coherent states
http://hdl.handle.net/2160/11209
Quantum filtering for systems driven by fields in single-photon states or superposition of coherent states
Gough, John Edward; James, Matthew R.; Nurdin, Hendra I.; Combes, Joshua
We derive the stochastic master equations, that is to say, quantum filters, and master equations for an arbitrary quantum system probed by a continuous-mode bosonic input field in two types of nonclassical states. Specifically, we consider the cases where the state of the input field is a superposition or combination of (1) a continuous-mode, single-photon wave packet and vacuum, and (2) any continuous-mode coherent states.
Funder: EPSRC RONO: EP/H016708/1
2012-10-15T00:00:00ZSingle Photon Quantum Filtering Using non-Markov Embeddings
http://hdl.handle.net/2160/11208
Single Photon Quantum Filtering Using non-Markov Embeddings
Gough, John Edward; James, Matthew R.; Nurdin, Hendra I.
We determine quantum master and filter equations for continuous measurement of systems coupled to input fields in certain non-classical continuous-mode states, specifically single photon states. The quantum filters are shown to be derivable from an embedding into a larger non-Markovian system, and are given by a system of coupled stochastic differential equations.
Gough, J. E., James, M. R., Nurdin, H. I. (2012). Single Photon Quantum Filtering Using non-Markov Embeddings. Philosophical Transactions of The Royal Society A Mathematical, Physical & Engineering Sciences, 370 (1979), 5241-5258.
2012-11-28T00:00:00ZOn structure-preserving transformations of the Itō generator matrix for model reduction of quantum feedback networks
http://hdl.handle.net/2160/11206
On structure-preserving transformations of the Itō generator matrix for model reduction of quantum feedback networks
Gough, John Edward; Nurdin, H. I.
Two standard operations of model reduction for quantum feedback networks, elimination of internal connections under the instantaneous feedback limit and adiabatic elimination of fast degrees of freedom, are cast as structure-preserving transformations of Itō generator matrices. It is shown that the order in which they are applied is inconsequential.
2012-11-28T00:00:00ZA Protocol For Cooling and Controlling Composite Systems by Local Interactions
http://hdl.handle.net/2160/11087
A Protocol For Cooling and Controlling Composite Systems by Local Interactions
Burgarth, Daniel; Giovannetti, Vittorio
Ericsson, Marie; Montangero, Simone
We discuss an explicit protocol which allows one to externally cool and control a composite system by operating on a small subset of it. The scheme permits to transfer arbitrary and unknown quantum states from a memory on the network ('upload access') as well as the inverse ('download access'). In particular it yields a method for cooling the system.
D. Burgarth, V. Giovannetti, A Protocol For Cooling and Controlling Composite Systems by Local Interactions, in 'Quantum Information and Many Body Quantum Systems', proceedings, M. Ericsson and S. Montangero (eds.), Pisa, Edizioni della Normale, p. 17 (2008)
2011-09-27T00:00:00Z