Tensor Representation of Spin States ; ; Baguette, Dorian et al in Physical Review Letters (2015), 114 We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most ... [more ▼] We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most important properties of Bloch vectors. Our representation, based on covariant matrices introduced by Weinberg in the context of quantum field theory, allows for a simple parametrization of coherent spin states, and a straightforward transformation of density matrices under local unitary and partial tracing operations. It enables us to provide a criterion for anticoherence, relevant in a broader context such as quantum polarization of light. [less ▲] Detailed reference viewed: 32 (15 ULg)Tensor Representation of Spin States ; ; Baguette, Dorian et al in Physical Review Letters (2015), 114 We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most ... [more ▼] We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most important properties of Bloch vectors. Our representation, based on covariant matrices introduced by Weinberg in the context of quantum field theory, allows for a simple parametrization of coherent spin states, and a straightforward transformation of density matrices under local unitary and partial tracing operations. It enables us to provide a criterion for anticoherence, relevant in a broader context such as quantum polarization of light. [less ▲] Detailed reference viewed: 32 (15 ULg)Tensor Representation of Spin States ; ; Baguette, Dorian et al in Physical Review Letters (2015), 114 We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most ... [more ▼] We propose a generalization of the Bloch sphere representation for arbitrary spin states. It provides a compact and elegant representation of spin density matrices in terms of tensors that share the most important properties of Bloch vectors. Our representation, based on covariant matrices introduced by Weinberg in the context of quantum field theory, allows for a simple parametrization of coherent spin states, and a straightforward transformation of density matrices under local unitary and partial tracing operations. It enables us to provide a criterion for anticoherence, relevant in a broader context such as quantum polarization of light. [less ▲] Detailed reference viewed: 32 (15 ULg); ; Baguette, Dorian et al in Physical Review Letters (2015), 114 Heisenberg-limited Metrology without Entanglement ; Martin, John in Research in Optical Sciences, OSA Technical Digest (2012) Detailed reference viewed: 16 (3 ULg)Heisenberg-limited metrology without entanglement ; Martin, John Conference (2012, March) Detailed reference viewed: 11 (0 ULg)Heisenberg-limited metrology without entanglement ; Martin, John Conference (2012, January) Detailed reference viewed: 13 (2 ULg)Multiqubit symmetric states with a high geometric entanglement Martin, John ; ; et al Poster (2011, May 25) We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric ... [more ▼] We propose a detailed study of the geometric entanglement properties of pure symmetric N-qubit states, focusing more particularly on the identification of symmetric states with a high geometric entanglement and how their entanglement behaves asymptotically for large N. We show that much higher geometric entanglement with improved asymptotical behavior can be obtained in comparison with the highly entangled balanced Dicke states studied previously. We also derive an upper bound for the geometric measure of entanglement of symmetric states. The connection with the quantumness of a state is discussed. [less ▲] Detailed reference viewed: 42 (9 ULg)Decoherence-enhanced measurements ; Martin, John Conference (2009, May) Detailed reference viewed: 13 (0 ULg)Interference in the light emitted by a single tunneling atom Martin, John ; Poster (2008, July) Detailed reference viewed: 5 (0 ULg)Spontaneous emission from a tunneling atom ; Martin, John Conference (2008, March) Detailed reference viewed: 6 (0 ULg)Spontaneous emission from a two-level atom tunneling in a double-well potential ; Martin, John in Physical Review. A (2008), 77 We study a two-level atom in a double-well potential coupled to a continuum of electromagnetic modes (black-body radiation in three dimensions at zero absolute temperature). Internal and external degrees ... [more ▼] We study a two-level atom in a double-well potential coupled to a continuum of electromagnetic modes (black-body radiation in three dimensions at zero absolute temperature). Internal and external degrees of freedom of the atom couple due to recoil during emission of a photon. We provide a full analysis of the problem in the long wavelengths limit up to the border of the Lamb-Dicke regime, including a study of the internal dynamics of the atom (spontaneous emission), the tunneling motion, and the electric field of the emitted photon. The tunneling process itself may or may not decohere depending on the wavelength corresponding to the internal transition compared to the distance between the two wells of the external potential, as well as on the spontaneous emission rate compared to the tunneling frequency. Interference fringes appear in the emitted light from a tunneling atom, or an atom in a stationary coherent superposition of its center-of-mass motion, if the wavelength is comparable to the well separation, but only if the external state of the atom is post selected. [less ▲] Detailed reference viewed: 27 (9 ULg)Coherent control of atomic tunnelling Martin, John ; in Journal of Physics B Atomic Molecular Physics (2008), 41 We study the tunnelling of a two-level atom in a double well potential while the atom is coupled to a single electromagnetic field mode of a cavity. The coupling between internal and external degrees of ... [more ▼] We study the tunnelling of a two-level atom in a double well potential while the atom is coupled to a single electromagnetic field mode of a cavity. The coupling between internal and external degrees of freedom, due to the mechanical effect on the atom from photon emission into the cavity mode, can dramatically change the tunnelling behaviour. We predict that in general the tunnelling process becomes quasiperiodic. In a certain regime of parameters a collapse and revival of the tunnelling occurs. Accessing the internal degrees of freedom of the atom with a laser allows us to coherently manipulate the atom position, and in particular to prepare the atom in one of the two wells. [less ▲] Detailed reference viewed: 24 (7 ULg) |
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