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– In this paper, a new decoy-state scheme for quantum key distribution with parametric down-conversion source is proposed. We use both three-intensity decoy states and their triggered and nontriggered components to estimate the fraction of single-photon counts and quantum bit-error rate of single-photon, and then deduce a more accurate value of key… (More)

- P. G. L. Porta Mana, Anders Månsson, Gunnar Björk
- ArXiv
- 2006

Probability-like parameters appearing in some statistical models, and their prior distributions, are reinterpreted through the notion of `circumstance', a term which stands for any piece of knowledge that is useful in assigning a probability and that satisfies some additional logical properties. The idea, which can be traced to Laplace and Jaynes, is that… (More)

- P. G. L. Porta Mana, Anders Månsson, Gunnar Björk
- ArXiv
- 2007

An approach to induction is presented, based on the idea of analysing the context of a given problem into 'circumstances'. This approach, fully Bayesian in form and meaning, provides a complement or in some cases an alternative to that based on de Finetti's representation theorem and on the notion of infinite exchangeability. In particular, it gives an… (More)

An approach to induction is presented, based on the idea of analysing the context of a given problem into 'circumstances'. This approach, fully Bayesian in form and meaning, provides a complement or in some cases an alternative to that based on de Finetti's representation theorem and on the notion of infinite exchangeability. In particular, it gives an… (More)

This is the first part of a three-note study which starts from an analysis of " probabilities of probabilities " to arrive at old and new state-assignment methods in classical and quantum mechanics. In this note, probability-like parameters appearing in some statistical models, and their prior distributions, are reinterpreted through the notion of… (More)

- Isabel Sainz, Gunnar Björk
- 2008

Dissipation may cause two initially entangled qubits to evolve into a separable state in a finite time. This behavior is called entanglement sudden death (ESD). We study to what extent quantum error correction can combat ESD. We find that in some cases quantum error correction can delay entanglement sudden death but in other cases quantum error correction… (More)

In this paper, we will show that a vanishing generalized concurrence of a separable state can be seen as an algebraic variety called the Segre variety. This variety define a quadric space which gives a geometric picture of separable states. For pure, bi-and three-partite states the variety equals the generalized concurrence. Moreover, we generalize the… (More)

- Roberth Asplund, Gunnar Björk, Mohamed Bourenanne
- 2000

We discuss a real-valued expansion of any Hermitian operator defined in a Hilbert space of finite dimension N , where N is a prime number, or an integer power of a prime. The expansion has a direct interpretation in terms of the operator expectation values for a set of complementary bases. The expansion can be said to be the complement of the discrete… (More)

- Mohamed Bourennane, Daniel Ljunggren, Iulia Ghiu, Gunnar Björk, Christian Mikkelsen
- 2001

This report summarises the ongoing work in QuComm on the demonstration of novel quantum communication protocols, in particular multi-party protocols or protocols which use more than 2-states (or more than one qubit). Such new protocols will extend the capabilities of quantum communication by increasing the channel capacity, by making the systems less… (More)

- Yuntian Chen, Gunnar Björk
- Quantum Information & Computation
- 2008