Second Annual MIT-Cambridge Quantum Information Workshop

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Contact: Timothy F. Havel

IAP Short Courses

(PDF of overheads available for some presentations from links in their abstracts below)

DATE & TIME
 9:00 – 10:30 AM 10:30 AM – Noon 2:00 – 3:30 PM 3:30 – 5:00 PM
Mon. Jan. 27TH
 D. Kuan Li Oi, Quantum Maps ...
C. Doran,
Applications of Geometric Algebra to Quantum Physics
Tue. Jan. 28TH C. Barnes,
Inside Quantum Devices
 A. Kent,
Topics in Quantum Cryptography
Y. Suhov & T. Voice,
Entanglement in Large Quantum Systems
Wed. Jan. 29TH M. Saracenos, Quantum Maps ...

Workshop Schedule

(events covered by two-way video link to DAMTP (MR11 in CMS) have headers with green background)

6:00 – 9:00 PM WEDNESDAY JANUARY 29TH IN BLDG E-52
Reception at the MIT Faculty Club
8:30 AM – 12:30 PM THURSDAY JANUARY 30TH IN ROOM 1-390
TIME
 MIT GROUP LEADER
 QUANTUM INFORMATION RESEARCH OVERVIEW
 8:30 am
 Seth Lloyd, Mech. Eng. / RLE Advances in Quantum Communication
 9:00 am
 David Cory & Tim Havel, Nucl. Eng. Ongoing and Upcoming Experiments in NMR/QIP
< Caffeine | Break > = 9:30 - 9:45 am
 9:45 am
 Leonid Levitov, Physics Adiabatic Transport and Entangled States
10:15 am
 Eddie Farhi & Jeff Goldstone, Physics Speedup by Quantum Walk
10:45 am
 Sanjoy Mitter, EECS / LIDS Continuous Quantum Measurement
< Caffeine | Break > = 11:15 - 11:30 am
11:30 am
 Terry Orlando, EECS / RLE
 Time-Ordered Measurements of the Two-States in a Niobium Superconducting Qubit
12:00 pm Jeff Shapiro & Franco Wong, EECS / RLE
 Long-Distance Quantum Communication: Architecture and Entanglement Sources
12:30 – 2:00 PM THURSDAY JANUARY 30TH IN BLDG E-52
Lunch at the MIT Faculty Club
2:00 – 6:00 PM THURSDAY JANUARY 30TH
Laboratory Tours (to be Arranged Individually over Lunch)
EVENING OF THURSDAY JANUARY 30TH
MIT People Take Cambridge People out to their Favorite Local Restaurant &/or Pub
8:30 – 11:30 AM FRIDAY JANUARY 31ST IN ROOM 1-390
Collective Brain-Storming Session (Caffeine Continuously Provided)
Based on What We Learned Yesterday, What Can We Do for One Another in the Future?
11:30 AM – 1:00 PM FRIDAY JANUARY 31ST
Chance to View Posters in 1-242 & Continue Brain-Storming on a One-to-One Basis (Refreshments Served)
1:30 – 3:30 PM FRIDAY JANUARY 31ST (PDF of MAP of WAYS to go...)
Visit the Exhibits at the Boston Muesum of Science (Recommendation: The Computing Revolution)
3:30 – 5:30 PM FRIDAY JANUARY 31ST
Early Dinner in Skyline Room at the Museum of Science
5:30 – 6:30 PM FRIDAY JANUARY 31ST
Laser Show at the Museum of Science (Tickets Provided)
REST OF THE EVENING FRIDAY JANUARY 31ST
Everybody Does Exactly What They Want
(Suggestions: Hang out in the Science Cafe; See "Mysteries of Egypt" in the Omnimax Theater; See "Stars of the Pharaohs" in the Planetarium; Or take the tram downtown and ...)


Abstracts

Advances in Quantum Communication

Seth Lloyd
(joint work with Vittorio Giovannetti, Lorenza Maccone, Michal Horodecki & P. Shor)

This talk presents new results in the theory of communication over noisy quantum channels, including the entanglement assisted capacity of noisy broad-band bosonic channels, and the use of random codes to transmit quantum information down noisy channels at a rate given by the coherent information.

Ongoing and Upcoming Experiments in NMR/QIP

David Cory & Joseph Emerson
(joint work with Nicolas Boulant, Paola Cappellaro, Debra Chen, Hyung-Joon Cho, Timothy F. Havel, Jonathan Hodges, Daniel Preda, Sekhar Ramanathan, Scott Sanders, Sid Sinha, Ketan Vyas, Yaakov Weinstein)

We will describe some of our ongoing and upcoming measurements on simple quantum information processors based on NMR.  These include:

Introductions and reviews of QIP by NMR are available on the quant-ph preprint archive [Cory et al. (2000); Havel et al (1998); Laflamme et al. (2002)] and in a recent article in Am. J. Phys. [70(2002), 345–62]. This work was supported in part by ARDA, the ARO, DARPA and the NSF.

Adiabatic Transport and Entangled States

Leonid Levitov

The coupling of 1D electrons to a surface acoustic wave (SAW) can be used as a vehicle to realize quantized adiabatic charge transport. We discuss the basic theory of this effect for Luttinger liquid system in carbon nanotubes and quantum wires.

Due to semi-metal character of nanotube band structure, the electron backscattering by a periodic SAW potential, which results in miniband formation, can be achieved at energies near the Fermi level.  Electron interaction is shown to reinforce minigaps and thereby improve current quantization. Quantized SAW induced current, as a function of electron density, changes sign at half-filling.

SAW-induced adiabatic transport in point contacts and quantum wires can be used to create entangled many-partricle electron states. We shall discuss the possibility to create electron pairs in a singlet spin state. A scheme for separating paired electrons without destrying singlet character of the state, "Einstein-Podolsky-Rosen pairs on a conveyor belt," will be described.

References:
1. V. I. Talyanskii, D. S. Novikov, B. D. Simons, L. S. Levitov, Quantized adiabatic charge transport in a carbon nanotube, Phys. Rev. Lett. v. 87 (27): 276802 (2001).
2. L. S. Levitov, V. I. Talyanskii, A. V. Shytov, to be published.

Speedup by Quantum Walk

Eddie Farhi & Jeff Goldstone
(joint work with Andrew M. Childs, Richard Cleve, Enrico Deotto, Sam Gutmann, and Daniel A. Spielman)

We will discuss the continuous time quantum walk and show how it achieves speedup over classical random walks.  We will also give an example of an oracular problem which requires exponential time for any classical algorithm but which can be solved in polynomial time by quantum walk [Childs et al., 2002].

Continuous Quantum Measurement

Sanjoy Mitter

In this talk I provide a model for continuous quantum measurement which leads to a Nonlinear Schroedinger-like equation describing the evolution of the quantum system under the action of continuous quantum measurements.

Time-Ordered Measurements of the Two-States in a Niobium Superconducting Qubit

Terry Orlando
(this is joint work with Ken Segall, Yang Yu,  Lin Tian, Donald Crankshaw, Daniel Nakada, Janice Lee, Bhuwan Singh, David Berns,  Bill Kaminsky, Brian Cord, S. Lloyd, and L.S. Levitov, MIT; with K. Berggren, MIT Lincoln Laboratory; and with M. Tinkham, Nina Markovic, Sergio O. Valenzuela,  Harvard University)

Measurements have been done on a superconducting persistent current qubit in the classical thermal activation regime and in the quantum regime. The superconducting qubit has states of equal and opposite circulating current. The resulting magnetization signal is read out by ramping the bias current of a DC SQUID magnetometer. This ramping causes time-ordered measurements of the two states, where one measurement of one state occurs before the other. This time-ordering results in an effective measurement time. Thermal activation measurements which exploit this effective measurement time reveal that the quality factor for the superconducting junctions are about a million, a value favorable for the observation of long coherence times at lower temperatures. Measurements at lower temperatures show the quantization of energy levels in these qubits.

This work is supported in part by the AFOSR grant F49620-01-1-0457 under the DoD University Research Initiative on Nanotechnology (DURINT) and by ARDA.

Long-Distance Quantum Communication: Architecture and Entanglement Sources

Jeffrey H. Shapiro & Franco N. C. Wong
(download PDF)

We will describe the basic architecture of a long-distance, high-fidelity quantum teleportation system based on polarization-entangled photons and trapped-atom quantum memories. Suitable polarization entanglement sources under development will be discussed.

This work was supported in part by the DoD MURI grant described at this URL, where numerous references are also available.

Applications of Geometric Algebra to Quantum Physics

Dr. Chris Doran, Astrophysics Group, Physics Dept., Cambridge Univ.
(download PDF for parts one, two, three & four)

This is an overview of the quantum physics part of a course given at Cambridge University, called "Physical Applications of Geometric Algebra". After a brief introduction to geometric algebra, we will study its role in the representations of single-particle spinors, before constructing multiparticle states and density operators. Applications to quantum information will be highlighted. Some mention will also be made of extending the main concepts to the relativistic setting, which raises interesting theoretical questions.

Topics in Quantum Cryptography

Adrian Kent, University of Cambridge, England
(download PDF)

These lectures look at the current state of the art in quantum cryptography applied to tasks which, unlike key distribution, are carried out between mistrustful parties. I focus in particular on known protocols, security proofs, and no-go theorems for bit commitment, coin tossing, and related tasks, and try to draw some general morals about the scope for research in quantum cryptography.

Inside Quantum Devices

Dr. Crispin H. W. Barnes, Solid-state Physics Group, Cambridge Univ., England
(download PDF)

This course will cover the following aspects of quantum devices:
(1) Band engineering / electrostatic confinement to reduce dimensionality 3->2->1->0; Landauer formalism for conductance; transport properties of 1D systems and quantum dots; Aharonov-Bohm effect; non-invasive measurement.
(2) Quantum Hall effect; edge states; quasi-particles; fractional quantum Hall effect / edge states; quantum anti-dots.
(3) The prospects for a quantum information processor based on these phenomena.