976 publications from this institution
Polarisation effects that can't be explained neither by polarisation mode dispersion (PMD) nor by polarisation dependent losses (PDL) alone have been. Moreover, theoretical models and simulations suggest that these combined PMD+PDL effects may significantly increase the fluctuations that come along with polarisation effects. We present measurements of BER fluctuations in a concatenation of PMD and PDL elements. The result confirms that combined PMD+PDL effects may introduce fluctuations larger than those estimated by simple rms rules
In John Stewart Bell and Twentieth-Century Physics: Vision and Integrity, fellow physicist Andrew Whitaker tells the story of Bell's life and his revolutionary discovery that not everything in physics can be explained using only local variables.
In order to study N-locality without inputs in long lines and in configurations with loops, e.g. the triangle, we introduce a natural joint measurement on two qubits different from the usual Bell state measurement. The resulting quantum probability $p(a_1,a_2,...,a_N)$ has interesting features. In particular the probability that all results are equal is that large, while respecting full symmetry, that it seems highly implausible that one could reproduce it with any N-local model, though - unfortunately - I have not been unable to prove it.
An improved plug & play interferometric system for quantum key distribution is presented. Self-alignment and compensation of birefringence remain, while limitations due to reflections are overcome. Original electronics implementing the BB84 protocol makes adjustment simple. Key creation with 0.1 photon per pulse at a rate of 325 Hz with a 2.9 percent QBER - corresponding to a net rate of 210Hz - over a 23 Km installed cable was performed.
Pseudo-telepathy is the most recent form of rejection of locality. Many of its properties have already been discovered: for instance, the minimal entanglement, as well as the minimal cardinality of the output sets, have been characterized. This paper contains two main results. First, we prove that no bipartite pseudo-telepathy game exists, in which one of the partners receives only two questions; as a corollary, we show that the minimal "input cardinality", that is, the minimal number of questions required in a bipartite pseudo-telepathy game, is 3x3. Second, we study the Bell-type inequality derived from the pseudo-telepathy game known as the Magic Square game: we demonstrate that it is a tight inequality for 3 inputs and 4 outputs on each side and discuss its weak resistance to noise.
Deeper insight leads to better practice. We show how the study of the foundations of quantum mechanics has led to new pictures of open systems and to a method of computation which is practical and can be used where others cannot. We illustrate the power of the new method by a series of pictures that show the emergence of classical features in a quantum world. We compare the development of quantum mechanics and of the theory of (biological) evolution.
A long range coherent OFDR is demonstrated by using a standard DFB laser diode coupled to an all fiber external double cavity. The optical frequency sweep was obtained by runing the phase of the feedback light. The laser linewidth reduction, tunability and mode hopping are also discussed.
Nicolas Gisin and Rob Thew, world leading researchers in quantum communication and authors of the invited Insight Letter ‘Quantum communication technologies’ on page 965, tell us why they enjoy their field
We investigate possible explanations of quantum correlations that satisfy the principle of continuity, which states that everything propagates gradually and continuously through space and time. In particular, following (Bancal et al. in Nat. Phys., 2012) we show that any combination of local common causes and direct causes satisfying this principle, i.e. propagating at any finite speed, leads to sig- nalling. This is true even if the common and direct causes are allowed to propagate at a supraluminal-but-finite speed defined in a Newtonian-like privileged univer- sal reference frame. Consequently, either there is supraluminal communication or the conclusion that Nature is nonlocal (i.e. discontinuous) is unavoidable. (Editor's note: for a video of the talk given by Prof. Gisin at the Aharonov-80 conference in 2012 at Chapman University, see quantum.chapman.edu/talk-28.)
Entanglement is the physical property that marks the most striking deviation of the quantum from the classical world. It has been mentioned first by the great Austrian Physicist Erwin Schr¨odinger in 1935 (an introduction to this and other quantum phenomena is given in [1]). Yet, despite this theoretical prediction now being 80 years old, and the famous experimental verifications by Alain Aspect dating back to the early eighties [2], entanglement and its use entered mainstream physics as a key element of quantum information science [3] only in the 1990’s.
