• Publications
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Perfect Transfer of Arbitrary States in Quantum Spin Networks
We propose a class of qubit networks that admit perfect state transfer of any two-dimensional quantum state in a fixed period of time. We further show that such networks can distribute arbitrary
Perfect state transfer : Beyond nearest-neighbor couplings
  • A. Kay
  • Physics
  • 9 September 2005
In this paper we build on the ideas presented in previous works for perfectly transferring a quantum state between opposite ends of a spin chain using a fixed Hamiltonian. While all previous studies
Basics of perfect communication through quantum networks
  • A. Kay
  • Mathematics, Physics
  • 11 February 2011
Perfect transfer of a quantum state through a one-dimensional chain is now well understood, allowing one not only to decide whether a fixed Hamiltonian achieves perfect transfer but to design a
Effects of reduced measurement independence on Bell-based randomness expansion.
TLDR
A no-signaling model with reduced "free will" is considered and the adversary’s capabilities in the task of randomness expansion are bound.
Optimal universal quantum cloning: asymmetries and fidelity measures
  • A. Kay
  • Mathematics, Physics
    Quantum Inf. Comput.
  • 18 July 2014
TLDR
All known results on optimal universal cloning are reproduced, and the recent results on asymmetric cloning are pushed much further, giving new trade-off relations between fidelities for broad classes of optimal cloning machines.
Perfect quantum routing in regular spin networks.
TLDR
The ability to route multiple states simultaneously and the regularity of the networks vastly improve the utility of this scheme in comparison to the task of state transfer, leading to an implementation in optical lattices.
Optimal detection of entanglement in Greenberger-Horne-Zeilinger states
  • A. Kay
  • Physics
  • 22 February 2011
We present a broad class of states which are diagonal in the basis of N-qubit GHZ states such that non-positivity under the partial transpose operation is necessary and sufficient for the presence of
Limited measurement dependence in multiple runs of a Bell test
The assumption of free will - the ability of an experimentalist to make random choices - is central to proving the indeterminism of quantum resources, the primary tool in quantum cryptography.
Capabilities of a perturbed toric code as a quantum memory.
  • A. Kay
  • Physics, Medicine
    Physical review letters
  • 20 July 2011
TLDR
It is proved that for a large class of perturbations, the survival time of stored information grows at least logarithmically with the system size, and randomizing the stabilizer strengths gives a polynomial survival time with a degree that depends on the strength of the perturbation.
Perfect and Pretty Good State Transfer for Field-Free Heisenberg Chains
In a one-dimensional Heisenberg chain, we show that there are no sets of coupling strengths such that the evolution perfectly transfers a quantum state between the two ends of the chain without the
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