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- R W Spekkens, Terry Rudolph
- Physical review letters
- 2002

We present a quantum protocol for the task of weak coin flipping. We find that, for one choice of parameters in the protocol, the maximum probability of a dishonest party winning the coin flip if the other party is honest is 1/sqrt[2]. We also show that if parties restrict themselves to strategies wherein they cannot be caught cheating, their maximum… (More)

- Robert W Spekkens
- Physical review letters
- 2008

Two notions of nonclassicality that have been investigated intensively are: (i) negativity, that is, the need to posit negative values when representing quantum states by quasiprobability distributions such as the Wigner representation, and (ii) contextuality, that is, the impossibility of a noncontextual hidden variable model of quantum theory. Although… (More)

- Robert W Spekkens, D H Buzacott, A J Keehn, Ben Toner, G J Pryde
- Physical review letters
- 2009

In a noncontextual hidden variable model of quantum theory, hidden variables determine the outcomes of every measurement in a manner that is independent of how the measurement is implemented. Using a generalization of this notion to arbitrary operational theories and to preparation procedures, we demonstrate that a particular two-party… (More)

- Robert W. Spekkens, Terry Rudolph
- Quantum Information & Computation
- 2002

Received (received date) Revised (revised date) It is well known that no quantum bit commitment protocol is unconditionally secure. Nonetheless, there can be non-trivial upper bounds on both Bob's probability of correctly estimating Alice's commitment and Alice's probability of successfully unveiling whatever bit she desires. In this paper, we seek to… (More)

A controversy that has arisen many times over in disparate contexts is whether quantum co-herences between eigenstates of certain quantities are fact or fiction. We present a pedagogical introduction to the debate in the form of a hypothetical dialogue between proponents from each of the two camps: a factist and a fictionist. A resolution of the debate can… (More)

Recently, there has been much interest in a new kind of " unspeakable " quantum information that stands to regular quantum information in the same way that a direction in space or a moment in time stands to a classical bit string: the former can only be encoded using particular degrees of freedom while the latter are indifferent to the physical nature of… (More)

- Fernando G S L Brandão, Michał Horodecki, Jonathan Oppenheim, Joseph M Renes, Robert W Spekkens
- Physical review letters
- 2013

The ideas of thermodynamics have proved fruitful in the setting of quantum information theory, in particular the notion that when the allowed transformations of a system are restricted, certain states of the system become useful resources with which one can prepare previously inaccessible states. The theory of entanglement is perhaps the best-known and most… (More)

- Bob Coecke, Bill Edwards, Robert W. Spekkens
- Electr. Notes Theor. Comput. Sci.
- 2011

- Iman Marvian, Robert W Spekkens
- Nature communications
- 2014

Noether's theorem is a fundamental result in physics stating that every symmetry of the dynamics implies a conservation law. It is, however, deficient in several respects: for one, it is not applicable to dynamics wherein the system interacts with an environment; furthermore, even in the case where the system is isolated, if the quantum state is mixed then… (More)

- J-C Boileau, D Gottesman, R Laflamme, D Poulin, R W Spekkens
- Physical review letters
- 2004

We present two polarization-based protocols for quantum key distribution. The protocols encode key bits in noiseless subspaces or subsystems and so can function over a quantum channel subjected to an arbitrary degree of collective noise, as occurs, for instance, due to rotation of polarizations in an optical fiber. These protocols can be implemented using… (More)