Gunnar Björk

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A fundamental notion of quantum mechanics is complementarity which expresses the fact that any quantum system has at least two properties that cannot simultaneously be known. One of these complementary property pairs, and perhaps the historically most important, is the wave-particle duality. A quantum system has both particle-like and wave-like properties.(More)
We propose an extension of quantum key distribution based on encoding the key into quNits, i.e. quantum states in an N-dimensional Hilbert space. We estimate both the mutual information between the legitimate parties and the eavesdropper, and the error rate, as a function of the dimension of the Hilbert space. We derive the information gained by an(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)
Mutually unbiased bases and discrete Wigner functions are closely, but not uniquely related. Such a connection becomes more interesting when the Hilbert space has a dimension that is a power of a primeN = d, which describes a composite system of n qudits. Hence, entanglement naturally enters the picture. Although our results are general, we concentrate on(More)
Morphologic analysis of spermatozoa recovered 10 hours postcoitally from the human female genital tract and its correlation to the clinical situation have shown that (1) spermatozoa in the vagina are equivalent to those in the semen sample; (2) spermatozoa within the cervical secretion exhibit significantly better morphology than do those of the semen(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)
A concensus conference on the timing of facial osteotomies was held in Jönköping, Sweden. Seven teams consisting of a maxillofacial surgeon and an orthodontist representing five countries discussed treatment planning for young patients with maxillomandibular deformities with special emphasis on timing. Patients with severe syndromic facial deformities were(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.
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)