• Publications
  • Influence
Quantum Theory From Five Reasonable Axioms
  • L. Hardy
  • Physics, Mathematics
  • 3 January 2001
The usual formulation of quantum theory is based on rather obscure axioms (employing complex Hilbert spaces, Hermitean operators, and the trace formula for calculating probabilities). In this paperExpand
No signaling and quantum key distribution.
TLDR
A key distribution scheme provably secure against general attacks by a postquantum eavesdropper limited only by the impossibility of superluminal signaling is described, which stems from violation of a Bell inequality. Expand
ARE QUANTUM STATES REAL
TLDR
This paper proves that ontic indifference must be violated in any model reproducing quantum theory in which the quantum state is not a real thing. Expand
Reformulating and Reconstructing Quantum Theory
  • L. Hardy
  • Mathematics, Physics
  • 11 April 2011
We provide a reformulation of finite dimensional quantum theory in the circuit framework in terms of mathematical axioms, and a reconstruction of quantum theory from operational postulates. TheExpand
Towards quantum gravity: a framework for probabilistic theories with non-fixed causal structure
  • L. Hardy
  • Mathematics, Physics
  • 9 August 2006
General relativity is a deterministic theory with non-fixed causal structure. Quantum theory is a probabilistic theory with fixed causal structure. In this paper, we build a framework forExpand
A formalism-local framework for general probabilistic theories, including quantum theory
  • L. Hardy
  • Physics, Computer Science
  • Mathematical Structures in Computer Science
  • 27 May 2010
TLDR
This paper provides a formalism that is local in the following very specific sense: calculations pertaining to any region of space–time employ only mathematical objects associated with that region, and shows how to put classical probability theory and quantum theory into this framework. Expand
Logical Bell Inequalities
TLDR
This paper introduces a notion of logical Bell inequality which can be used to systematically derive testable inequalities for a very wide variety of situations, and shows how the logical robustness can be converted into systematic, general derivations of inequalities with provable violations. Expand
Cheat sensitive quantum bit commitment.
  • L. Hardy, A. Kent
  • Computer Science, Medicine
  • Physical review letters
  • 9 November 1999
TLDR
An unconditionally secure cheat sensitive nonrelativistic bit commitment protocol which uses quantum information to implement a task which is classically impossible; a simple relativistic protocol is described. Expand
Why Quantum Theory
  • L. Hardy
  • Mathematics, Physics
  • 12 November 2001
The usual formulation of quantum theory is rather abstract. In recent work I have shown that we can, nevertheless, obtain quantum theory from five reasonable axioms. Four of these axioms areExpand
Substituting a qubit for an arbitrarily large number of classical bits.
TLDR
It is shown that a qubit can be used to substitute for a classical analog system requiring an arbitrarily large number of classical bits to represent digitally and no finite amount of one-way classical communication can perfectly simulate the effect of quantum entanglement. Expand
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