“Squashed entanglement”: An additive entanglement measure
- M. Christandl, A. Winter
- Computer Science, Mathematics
- 16 August 2003
A new entanglement monotone for bipartite quantum states is presented, inspired by the so-called intrinsic information of classical cryptography and is given by the halved minimum quantum conditional mutual information over all tripartite state extensions: it is convex, additive on tensor products, and superadditive in general.
Perfect state transfer in quantum spin networks.
- M. Christandl, N. Datta, A. Ekert, A. Landahl
- PhysicsPhysical Review Letters
- 17 September 2003
It is shown that 2log3N is the maximal perfect communication distance for hypercube geometries if one allows fixed but different couplings between the qubits, then perfect state transfer can be achieved over arbitrarily long distances in a linear chain.
The uncertainty principle in the presence of quantum memory
- M. Berta, M. Christandl, R. Colbeck, J. Renes, R. Renner
- Physics
- 7 September 2009
The Heisenberg uncertainty principle bounds the uncertainties about the outcomes of two incompatible measurements on a quantum particle. This bound, however, changes if a memory device is involved…
A hierarchy of topological tensor network states
- O. Buerschaper, J. M. Mombelli, M. Christandl, M. Aguado
- Physics
- 29 July 2010
We present a hierarchy of quantum many-body states among which many examples of topological order can be identified by construction. We define these states in terms of a general, basis-independent…
One-and-a-Half Quantum de Finetti Theorems
- M. Christandl, R. König, G. Mitchison, R. Renner
- Mathematics
- 15 February 2006
When n − k systems of an n-partite permutation-invariant state are traced out, the resulting state can be approximated by a convex combination of tensor product states. This is the quantum de Finetti…
Perfect Transfer of Arbitrary States in Quantum Spin Networks
- M. Christandl, N. Datta, T. Dorlas, A. Ekert, A. Kay, A. Landahl
- Physics
- 2 November 2004
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…
The Structure of Bipartite Quantum States - Insights from Group Theory and Cryptography
- M. Christandl
- Physics
- 1 April 2006
This thesis presents a study of the structure of bipartite quantum states. In the first part, the representation theory of the unitary and symmetric groups is used to analyse the spectra of quantum…
Postselection technique for quantum channels with applications to quantum cryptography.
- M. Christandl, R. König, R. Renner
- Mathematics, Computer SciencePhysical Review Letters
- 17 September 2008
A general method for studying properties of quantum channels acting on an n-partite system, whose action is invariant under permutations of the subsystems, and a simple proof for the fact that security of a discrete-variable quantum key distribution protocol against collective attacks implies security of the protocol against the most general attacks.
Quantum Anonymous Transmissions
- M. Christandl, S. Wehner
- Computer Science, MathematicsInternational Conference on the Theory and…
- 28 September 2004
A quantum protocol for sending and receiving classical bits anonymously, which is completely traceless: it successfully prevents later reconstruction of the sender and introduces a new primitive called anonymous entanglement, which may be useful in other contexts as well.
The Quantum Reverse Shannon Theorem Based on One-Shot Information Theory
- M. Berta, M. Christandl, R. Renner
- Computer Science
- 20 December 2009
A new proof of the Quantum Reverse Shannon Theorem is provided, which has been proved by Bennett, Devetak, Harrow, Shor, and Winter and is based on two recent information-theoretic results: one-shot Quantum State Merging and the Post-Selection Technique for quantum channels.
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