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2005 March

Archive for March, 2005

The impossibility of noncontextual hidden variable models of quantum theory and its significance for quantum information

Monday, March 21st, 2005

Date: April 1, 2005

Who: Rob Spekkens (Perimeter Institute)

Seminar type: Research

Abstract:
The Bell-Kochen-Specker theorem establishes the impossibility of a noncontextual hidden variable model of quantum theory. I will argue for an operational definition of contextuality that generalizes the standard notion in three ways: (1) it applies to arbitrary operational theories rather than just quantum theory, (2) it applies to arbitrary experimental procedures rather than just sharp measurements, and (3) it applies to a broad class of ontological models of quantum theory rather than just deterministic hidden variable models. Three new no-go theorems can then be derived, each based on an assumption of noncontextuality for a different sort of experimental procedure; one for preparation procedures, another for unsharp measurement procedures (that is, measurement procedures associated with positive-operator valued measures), and a third for transformation procedures. I will present one of these proofs in detail, and discuss the extent to which the information-processing advantages of quantum systems relative to their classical counterparts might be due to contextuality.

Suggested reading:

  • N. D. Mermin, “Hidden variables and the two theorems of John Bell”, Rev. Mod. Phys. 65, 803 (1993)
  • R. W. Spekkens, “Contextuality for preparations, transformations, and
    unsharp measurements”, quant-ph/0406166

Research Fellowship

Wednesday, March 16th, 2005

The Quantum Information Science group at the University of Queensland is looking to appoint an outstanding researcher to a Research Fellowship for between 3 and 5 years.

A detailed description of the position and application procedure is available here. I encourage strong applicants in quantum information science and related areas to consider applying. (Note that the level of the position is somewhat higher than the positions described in my previous post.)

The closing date for applications is April 15, 2005.

Please pass a link to this message on to any parties you believe may be interested.

Postdoctoral Fellowships available

Wednesday, March 16th, 2005

Each year the University of Queensland offers a limited number of postdoctoral fellowships for qualified applicants. Several members of the Quantum Information Science group have been past recipients.

These are nice fellowships. They are typically awarded for three years, have a small grant attached to allow the recipient to travel and host visitors, and afford a fair measure of independence, since they are awarded by the University, not by any individual Faculty member.

The 2006 call for applications is now available, and I encourage strong candidates [*] in quantum information science or a closely related area to consider applying. Applications close April 29, 2005.

Please contact me if you’re interested in applying.

Note that applications are to be made directly to the University, not to me.

Please pass a link to this message on to any parties you believe may be interested.

[*] In practice, this usually means having at least several published papers in refereed journals of high standing.

Quantum Information Visiting Fellowships at the University of Queensland

Wednesday, March 16th, 2005

Note: Please pass word of this program on to anyone you think may be interested.

The theoretical Quantum Information Science group at the University of Queensland is inviting expressions of interest from graduate students and early career researchers (up to eight years out of PhD) interested in visiting the group for 3-5 weeks during 2005.

About the group: The Quantum Information Science group currently has four faculty members (Andrew Doherty, Gerard Milburn, Michael Nielsen, Tim Ralph), 5 postdocs, and 14 PhD students. Group members collaborate closely with the experimental groups of Andrew White (quantum technology lab) and Halina Rubinsztein-Dunlop (BEC and quantum dots), the theoretical condensed matter group of Ross McKenzie, and the Queensland node of the Centre of Excellence for Quantum and Atom Optics. Fellows will be encouraged to interact broadly during their visit.

Duration: Fellowships will normally last for three to five weeks.

Background of Fellows

Graduate Students: Fellows will be currently working towards a PhD in quantum information science or a closely related field.

Early Career Researchers: Fellows should have a strong interest in quantum information science, but in some instances their background may be primarily in other areas of science, e.g., control theory, pure mathematics, theoretical computer science, condensed matter physics, quantum optics, high-energy physics, or other fields with a potential to contribute to the group.

We encourage applications from potential Fellows in all areas of science (computer science, mathematics, physics, engineering, chemistry) relevant to quantum information science.

Time: We aim to spread the Fellows out during 2005. For this reason, we ask that applicants think seriously about what dates they would be available to take up the Fellowship, and indicate those dates on the expression of interest.

Number: Up to 20 Fellowships will be awarded in 2005, 10 to graduate students, and 10 to early career researchers. The initial round of applications will be due March 18; depending on the quality and number of applications a further round may be held later in the year.

Benefits: The Fellowship will cover: the cost of a return economy class airfare by the most direct route from the recipient’s home institution to Brisbane, Australia; the cost of accommodation while in Brisbane; and the cost of transport to and from the airport. Please note that no salary or stipend will be provided.

Research seminar: Fellows will be asked to present a 40 minute whiteboard seminar about their ongoing research.

Tutorial lectures: Fellows will be asked to present a series of 2-4 tutorial lectures on some topic they nominate, for presentation at an informal whiteboard seminar series. These could come from a very wide range of areas, and would not be restricted to quantum information science. The following list of examples is simply meant to be suggestive: applicants should ask themselves what specialist knowledge they have that might be of interest to others.

  • Computer science: The status of the P versus NP problem; pseudorandom generators; derandomization; expander graphs; Markov chain Monte Carlo; PCP.
  • Control theory: open loop control; feedback control; complete controllability; Pontryagin maximum principle; Bellman equation.
  • Mathematics: topics in advanced linear algebra; Lie groups; Hopf algebras; quantum groups.
  • Complex systems: small worlds; network theory; self-organized criticality; information markets.
  • Condensed matter physics: quantum Hall effect; Bose-Einstein condensation; Mott insulater phase transition; superfluidity; superconductivity; high-temperature superconductivity; quantum phase transitions in general.
  • Other areas: Virtually any well-presented topic in any area of fundamental interest in computer science, mathematics and physics will be well-received.

Expression of interest

Please cut and paste the following into email, fill it out, and send to Michael Nielsen at nielsen@physics.uq.edu.au with the subject “Visiting Fellowship application”. Applications must be received by March 18 to be eligible; late applications will not be accepted.

Name:

Current position:

Supervisor (for grad student):

Thesis topic (for grad student):

Institution:

Current interests:

Past interests:

List up to three papers you’ve published in the past three years:

Desired duration of visit (3-5 weeks):

Dates you would able to visit (between April 15 and December 31, 2005):

Examples of three topics you’d be willing to give a short series (2-4) of tutorial seminars on. Note that this list is not binding; it’s simply meant to indicate the range of your expertise.

Capacities of Quantum Channels and How to Find Them

Friday, March 11th, 2005

Date: 18 March, 2005 (tentative)

Who: Yeong Cherng Liang (UQ)

Seminar type: Journal club

Abstract:
We survey what is known about the information transmitting capacities of quantum channels, and give a proposal of how to calculate some of these capacities using linear programming.

Background:

Entanglement of zero angular momentum mixtures and black hole entropy

Monday, March 7th, 2005

Date: 11 March, 2005

Who: Danny Terno (Perimeter Institute)

Seminar type: Research

Background: quant-ph/0502043