Gunnar Björk

Learn More
In this Letter we experimentally implement a single photon Bell test based on the ideas of S. Tan et al. [Phys. Rev. Lett. 66, 252 (1991)]] and L. Hardy [Phys. Rev. Lett. 73, 2279 (1994)]]. A double homodyne measurement is used to measure correlations in the Fock space spanned by zero and one photons. Local oscillators used in the correlation measurement(More)
– 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)
We demonstrate a systematic approach to Heisenberg-limited lithographic image formation using four-mode reciprocal binomial states. By controlling the exposure pattern with a simple bank of birefringent plates, any pixel pattern on a (N+1) x (N+1) grid, occupying a square with the side half a wavelength long, can be generated from a 2N-photon state.
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)
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)
We have experimentally demonstrated a realization of the two-mode relative phase operator introduced by Luis and Sánchez-Soto (Luis A and Sánchez-Soto L L 1993 Phys. Rev. A 48 4702). The relative phase distribution function was measured for a weakly excited relative phase eigenstate and weakly excited two-mode coherent states. The experiment is also (using(More)
The theory of autocorrelation-function evaluation in fluorescence correlation spectroscopy is applied to a Lorentzian intensity distribution. An analytical solution to the autocorrelation function for diffusion is deduced for this spatial distribution. Experimental investigation of the distribution is performed using an enlarged detector aperture in a(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)
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)