February 27, 2014:
Cats, Decoherence and Quantum Measurement
by
Amir O. Caldeira, Universidade Estadual de Campinas  Instituto de Física "Gleb Wataghin"


March 13, 2014:
Nonquantum Entanglement and Bell Violation Analogs
by
Joseph Eberly, Center for Coherence and Quantum Optics, University of Rochester


July 03, 2014:
Quantum Photonics: Perspectives and challenges
by
John Rarity, University of Bristol


August 19, 2014:
A Mixture of Fermi and Bose Superfluids
by
Christophe Salomon, Laboratoire Kastler Brossel, Ecole Normale Supérieure, Paris, France


September 4, 2014:
A single ion in a Penning Trap: Test of QED and a new value for the electron´s mass
by
Guenter Werth, Johannes Gutenberg University, Mainz/Germany


October 15, 2014:
Matter and Light: sharing ideas and concepts in the quantum world
by
Gianni Blatter, ETH Zurich


November 7, 2014:
An atomic superfluid BoseEinstein condensate in a ring
by
William D. Phillips, Nobel Prize in Physics 1997, National Institute of Standards and Technology, University of Maryland


December 8, 2014:
CQT Annual Symposium: The Famous, The Bit & The Quantum
Quantum information and the monogamy of entanglement
by Aram Harrow, MIT
The Quantum Way of Doing Computations
by Rainer Blatt, University of Innsbruck
Random for whom?
by Valerio Scarani, CQT, NUS


Date: 27 Febuary 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: Amir O. Caldeira, Universidade Estadual de Campinas  Instituto de Física "Gleb Wataghin"
Title: Cats, Decoherence and Quantum Measurement
Abstract:
In this talk it is our intention to review the basic ideas of how entanglement relates to the socalled Schrödinger cat state and present a paradigmatic situation where states very similar to that one can be created. The example we have chosen is the SQUID ring which depending on the external bias allows us to implement a wealth of interesting physical situations to be treated.
We shall argue that in these situations the question of dissipation is really relevant and the concept of decoherence naturally arises.
Once we have accomplished that we discuss some possible implications of decoherence to the quantum theory of measurement . As a matter of fact, we shall employ an alternative measure of quantum correlation which goes beyond entanglement – the quantum discord – with the same purpose. We finally present recent experimental results performed with twin photons which corroborate our predictions.
This Colloquium is jointly organised with Graphene Research Centre, NUS.
Date: 13 March 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: Joseph Eberly, Center for Coherence and Quantum Optics, University of Rochester
Nonquantum Entanglement and Bell Violation Analogs
Abstract:
We are interested in nonquantum entanglement in the context of probabilistic classical theories. We will examine a category of correlation measurements in statistical optics prompted by the following remark of John Bell: "It can indeed be shown that that the quantum mechanical correlations cannot be reproduced by a hidden variables theory even if one allows a 'local' sort of indeterminism. ... This would not work."
Date: 03 July 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: John Rarity, University of Bristol
Quantum Photonics: Perspectives and challenges
Abstract:
I will review the status of quantum photonics focussing on the recent developments in spontaneous four wave mixing (FWM) in optical fibre1,2 and in silicon waveguides3. I will show that 4photon and 6photon experiments are now achievable with fibre sources but also that the scalability is primarily limited by loss. This is illustrated by recent 6N00N interferometry demonstrations4 and a variety of cluster state based experiments5. In all experiments to date quantum advantage can be inferred within a detection postselected subset of photons but this detection rate drops exponentially with increasing photon number. The integration of all components onto one chip could bring very large photon number experiments closer if waveguide, switching and detector losses can be made small. A future roadmap to making scalable quantum processors with linear optics resources is beginning to form but will require significant resource overhead. I will comment on emerging alternatives to linear optics approaches based on one dimensional cavities and waveguides that could reduce this overhead significantly6.
[1] McMillan,et al Narrowband highfidelity allfibre source of heralded single photons at 1570 nm, Opt. Express 17, 61566165 (2009).
[2] Halder, et al, Nonclassical 2photon interference with separate intrinsically narrowband fibre sources, Opt. Express 17, 46704676 (2009).
[3] Silverstone, et al, Onchip quantum interference between two silicon waveguide sources, Nature Photonics 8, 104 (2014).
[4] Bell, et al, MultiColour Quantum Metrology with Entangled Photons, Phys. Rev. Letts. 111, 093603 (2013).
[5] Bell, et al, Experimental characterization of universal oneway quantum computing, New J. Phys. 15, 053030 (2013).
[6] Young et al, Polarization engineering in photonic crystal waveguides for spinphoton entanglers, arXiv 1406.0714
Date: 19 August 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: Christophe Salomon, Laboratoire Kastler Brossel, Ecole Normale Supérieure, Paris, France
A Mixture of Fermi and Bose Superfluids
Abstract:
Superconductivity and superfluidity are spectacular macroscopic manifestations of genuine quantum collective effects with, today, vast domains of applications. In this family of quantum solids or fluids, ultracold gases and polaritons are the last born. Thanks to the great flexibility of laser cooling and trapping methods, ultracold gases offer to study these quantum correlated systems with a new twist. It is possible for instance to tune the strength and sign of the interaction between atoms. Optical lattices, realized by interfering laser beams, create periodic optical potentials that mimic the crystalline potential seen by electrons in solids.
In liquid helium and dilute gases, Bose and Fermi superfluidity has been observed separately, but producing a mixture where both the fermionic and the bosonic components are superfluid has been challenging. In this talk, we will describe the production of such a mixture of Bose and Fermi superfluids with dilute gases of two Lithium isotopes, 6Li and 7Li [1]. The mixture is remarkably stable and we probe the collective dynamics of this system by exciting centerofmass oscillations that exhibit extremely low damping below a certain critical velocity. Using high precision spectroscopy of these modes we observe coherent energy exchange and measure the coupling between the two superfluids. Our observations can be captured theoretically using a sumrule approach that we interpret in terms of two coupled oscillators. Tuning the attractive interaction in the Fermi superfluid, we measure the two speeds of sound in the mixture in the crossover between BEC of deeply bound dimers and BCS superfluidity. This provides a new method to probe the equation of state of the Fermi superfluid.
[1] I. FerrierBarbut, M. Delehaye, S. Laurent, A. Grier, M. Pierce, B. Rem, F. Chevy, C. Salomon, ArXiv :1404.2548
Date: 4 September 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: Guenter Werth, Johannes Gutenberg University, Mainz/Germany
A single ion in a Penning Trap: Test of QED and a new value for the electron´s mass
Abstract:
The magnetic moment of the electron bound in hydrogenlike ions has been measured with high precision. We perform Zeemanspectroscopy using single ions confined in a triplePenning trap. The results are compared with QED calculations and represent to date the most precise QED test in bound systems. From a comparison of theory and experiment in C5+ where QED contributions are small and well known, we derive a value for the electron´s atomic mass which is more than one order of magnitude more precise than previously known.
References:
S. Sturm et al., g Factor of Hydrogenlike 28Si13+, Phys. Rev. Lett. 107, 023002 (2011)
S. Sturm et a,, High precision measurement of the atomic mass of the electron, Nature 506, 467 (2014)
Date: 15 October 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: Gianni Blatter, ETH Zurich
Matter and Light: sharing ideas and concepts in the quantum world
Abstract:
With the development of quantum engineering, the traditionally separated fields of condensed matter physics and quantum optics are exchanging ideas and concepts to their mutual benefit. In the first part of the talk, I will recap the development of electronic structure theory in materials from weak to strong interactions and then discuss how ideas on strong correlations have penetrated into cold atomic physics and cavity optics in the last decade. In the second part I will discuss a reverse example, how ideas on entanglement, typically a realm of quantum optics, have started to penetrate into mesoscopic physics and define the new field of electronic optics.
Date: 7 November 2014, 4pm
Venue: CQT Seminar Room, S150315
Speaker: William D. Phillips, Nobel Prize in Physics 1997, National Institute of Standards and Technology, University of Maryland
An atomic superfluid BoseEinstein condensate in a ring
Abstract:
We create an atomicgas BoseEinstein condensate in a ringshaped trap and interrupt the circulation in the ring with a repulsive barrier. This system can exhibit behavior similar to that of a superconducting loop interrupted by a weak link or Josephson junction. We observe controllable, discrete phase slips (jumps in the phase winding number around the ring) and hysteretic behavior in such a system. A novel interference measurement can detect the presence, direction, and winding number of the circulation in the ring as well as provide a determination of the currentphase relationship of the weak link.