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40. QUANTUM INFORMATION TECHNOLOGIES

Quantum interference of a single spin excitation with a macroscopic atomic ensemble

Mon, 2014-01-06 15:36 - Kasper Jensen
Date: 
2014-03-03
Author(s): 

S. L. Christensen, J.-B. Béguin, E. Bookjans, H. L. Sørensen, J. H. Müller, J. Appel, E. S. Polzik

Reference: 

Phys. Rev. A 89, 033801 (2014),
arXiv:1309.2514 (2013)

URL: 

http://journals.aps.org/pra/abstract/10.1103/PhysRevA.89.033801

Quantum crystal growing: adiabatic preparation of a bosonic antiferromagnet in the presence of a parabolic inhomogeneity

Mon, 2013-05-06 15:40 - Mattia Giardini
Date: 
2013-03-21
Author(s): 

Søren Gammelmark and André Eckardt

Reference: 

New J. Phys. 15 033028 doi:10.1088/1367-2630/15/3/033028

URL: 

http://iopscience.iop.org/1367-2630/15/3/033028/

We theoretically study the adiabatic preparation of an antiferromagnetic phase in a mixed Mott insulator of two bosonic atom species in a one-dimensional optical lattice. In such a system one can engineer a tunable parabolic inhomogeneity by controlling the difference of the trapping potentials felt by the two species.

Measurement-induced two-qubit entanglement in a bad cavity: Fundamental and practical considerations

Mon, 2013-05-06 15:27 - Mattia Giardini
Date: 
2012-03-21
Author(s): 

Brian Julsgaard and Klaus Mølmer

Reference: 

URL: http://link.aps.org/doi/10.1103/PhysRevA.85.032327
DOI: 10.1103/PhysRevA.85.032327
PACS: 03.67.Bg, 42.50.Pq, 42.50.Lc, 03.65.Ta

An entanglement-generating protocol is described for two qubits coupled to a cavity field in the bad-cavity limit. By measuring the amplitude of a field transmitted through the cavity, an entangled spin-singlet state can be established probabilistically. Both fundamental limitations and practical measurement schemes are discussed, and the influence of dissipative processes and inhomogeneities in the qubits are analyzed.

Squeezing of collective excitations in spin ensembles

Mon, 2013-05-06 15:11 - Mattia Giardini
Date: 
2012-10-22
Author(s): 

Christian Kraglund Andersen and Klaus Mølmer

Reference: 

URL: http://link.aps.org/doi/10.1103/PhysRevA.86.043831
DOI: 10.1103/PhysRevA.86.043831
PACS: 42.50.Pq, 42.50.Lc, 42.50.Ct, 03.67.Bg

We analyze the possibility of creating two-mode spin squeezed states of two separate spin ensembles by inverting the spins in one ensemble and allowing spin exchange between the ensembles via a near resonant cavity field. We investigate the dynamics of the system using a combination of numerical and analytic calculations, and we obtain squeezing for a wide range of parameters.

Dynamical evolution of an inverted spin ensemble in a cavity: Inhomogeneous broadening as a stabilizing mechanism

Mon, 2013-05-06 15:08 - Mattia Giardini
Date: 
2012-12-07
Author(s): 

Brian Julsgaard and Klaus Mølmer

Reference: 

URL: http://link.aps.org/doi/10.1103/PhysRevA.86.063810
DOI: 10.1103/PhysRevA.86.063810
PACS: 42.50.Pq, 42.50.Ct, 42.50.Nn

We study the evolution of an inverted spin ensemble coupled to a cavity. While the inversion itself presents an inherent instability in the system, the inhomogeneous broadening of spin-resonance frequencies provides a stabilizing mechanism. The detailed behavior of mean values and variances of the spin components and the cavity field is accounted for under both stable and unstable conditions.

Demonstration of UV-written waveguides, Bragg gratings and cavities at 780nm, and an original experimental measurement of group delay

Wed, 2011-12-07 16:03 - Donatella Rosetti
Date: 
2011-11-22
Author(s): 

G. Lepert, M. Trupke, E.A. Hinds, H. Rogers, J.C. Gates, P.G.R. Smith

Reference: 

Optics Express, 19 (2011)
http://dx.doi.org/10.1364/OE.19.024933

We present direct UV-written waveguides and Bragg gratings operating at 780 nm. By combining two gratings into a Fabry-Perot cavity we have devised and implemented a novel and practical method of measuring the group delay of Bragg gratings.

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