Browsing Quantum Systems, Information and Control by Title

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Browsing Quantum Systems, Information and Control by Title

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  • Lapasar, Elham Hosseini; Maruyama, Koji; Burgarth, Daniel Klaus; Takui, Takeji; Kondo, Yasushi; Nakahara, Mikio (2012-01-23)
    It has been shown that inter-spin interaction strengths in a spin-1/2 chain can be evaluated by accessing one of the edge spins only. We demonstrate this experimentally for the simplest case, a three-spin chain, with the ...
  • Gough, John E. (2004-03)
    We consider an atomic beam reservoir as a source of quantum noise. The atoms are modelled as two-state systems and interact one-at-a-time with the system. The Floquet operators are described in terms of the Fermionic ...
  • Burgarth, Daniel Klaus; Maruyama, Koji (2009-10-07)
    Identifying the many-body Hamiltonian of a large quantum system is essential in understanding many physical phenomena, yet extremely difficult in general. We show that coupling strengths in networks of spin-1/2 particles ...
  • Burgarth, Daniel; Maruyama, Koji; Nori, Franco (2011-01-14)
    A number of many-body problems can be formulated using Hamiltonians that are quadratic in the creation and annihilation operators. Here, we show how such quadratic Hamiltonians can be efficiently estimated indirectly, ...
  • Burgarth, Daniel Klaus; Bose, Sougato; Bruder, Christoph; Giovannetti, Vittorio (2009)
    We give a sufficient criterion that guarantees that a many-body quantum system can be controlled by properly manipulating the (local) Hamiltonian of one of its subsystems. The method can be applied to a wide range of ...
  • Heule, Rahel; Bruder, Christoph; Burgarth, Daniel; Stojanović, Vladimir M. (2010)
    Motivated by some recent results of quantum control theory, we discuss the feasibility of local operator control in arrays of interacting qubits modeled as isotropic Heisenberg spin chains. Acting on one of the end spins, ...
  • Bayat, Abolfazl; Burgarth, Daniel Klaus; Mancini, Stefano; Bose, Sougato (2008-05-22)
    We investigate the multiple use of a ferromagnetic spin chain for quantum and classical communications without resetting. We find that the memory of the state transmitted during the first use makes the spin chain a ...
  • Evans, Dafydd Gwion; Gough, John Edward; James, Matthew (2012-11-07)
    We show that the series product, which serves as an algebraic rule for connecting state-based input/output systems, is intimately related to the Heisenberg group and the canonical commutation relations. The series product ...
  • Köstler, Claus; Speicher, Roland (2009-12-31)
    We showthat the classical de Finetti theorem has a canonical noncommutative counterpart if we strengthen 'exchangeability' (i.e., invariance of the joint distribution of the random variables under the action of the permutation ...
  • Köstler, Claus (2010-02-15)
    The extended de Finetti theorem characterizes exchangeable infinite sequences of random variables as conditionally i.i.d. and shows that the apparently weaker distributional symmetry of spreadability is equivalent to ...
  • Köstler, Claus (2011-01-31)
    Inspired by Lehner's results on exchangeability systems in [Leh06] we define `weak conditional freeness' and `conditional freeness' for stationary processes in an operator algebraic framework of noncommutative probability. ...
  • Gough, John Edward; Nurdin, H. I. (2012-11-28)
    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 ...
  • Gough, John E. (World Scientific, 2008-11-12)
    We consider the problem of optimal feedback control of a quantum system with linear dynamics undergoing continual non-demolition measurement of position and/or momentum, or both together. Specically, we show that a stable ...
  • Burgarth, Daniel; Giovannetti, Vittorio (2011-09-27)
    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 ...
  • Gough, John E.; James, Matthew R. (IEEE, 2008-12-09)
    The purpose of this paper is to discuss how Willems’ behavioral modeling might be applied to physical systems governed by the laws of quantum physics. A quantum behavior is simply defined in terms of the evolution of ...
  • Zhang, Jingfu; Burgarth, Daniel; Ditty, Michael; Ryan, Colm A.; Chandrashekar, C. M.; Laforest, Martin; Moussa, Osama; Baugh, Jonathan; Laflamme, Raymond (2009-06-16)
    We implement an iterative quantum state transfer exploiting the natural dipolar couplings in a spin chain of a liquid-crystal NMR system. During each iteration, a finite part of the amplitude of the state is transferred ...
  • Burgarth, Daniel Klaus; Giovannetti, Vittorio (2010-08-19)
    In this addendum to our paper [ D. Burgarth and V. Giovannetti Phys. Rev. Lett. 99 100501 (2007)] we prove that during the transformation that allows one to enforce control by relaxation on a quantum system, the ancillary ...
  • James, Matthew R.; Gough, John Edward (2010-08-01)
    The purpose of this paper is to extend J.C. Willems' theory of dissipative systems to open quantum systems described by quantum noise models. This theory, which combines ideas from quantum physics and control theory, ...
  • Gough, John Edward; Guta, Madalin I.; James, Matthew R.; Nurdin, Hendra I. (2011)
    Recent developments in quantum technology mean that is it now possible to manipulate systems and measure fermion elds (e.g. reservoirs of electrons) at the quantum level. This progress has motivated some recent work on ...
  • Gough, John Edward; James, Matthew R.; Nurdin, Hendra I.; Combes, Joshua (2012-10-15)
    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, ...

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