R. G. Herb Condensed Matter Seminars |
Events During the Week of January 25th through February 1st, 2015
Monday, January 26th, 2015
- Faculty Candidate Seminar
- From Quantum Communications to Small Quantum Computers
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin Hall
- Speaker: Graeme Smith, IBM TJ Watson Research Center
- Abstract: Physical information carriers obey quantum laws. Taking proper account of this fact has led over the past few decades to profound generalizations of both communication and computation theory. First, I’ll discuss the central question in the theory of quantum communication: What are the capabilities of a noisy quantum communication link? Addressing this question leads us to concepts like entanglement, a fundamentally quantum form of correlations which turns out to be a remarkably useful resource, new capabilities such as unconditionally secure cryptographic key agreement, and classically impossible kinds of synergy between independent communication links. Second, I’ll discuss two key questions in the race to build a quantum computer: what can we do with a small quantum computer, and how can we know that we’ve done it? These will be central questions in the coming decade as the size of quantum computing experiments begins to outstrip our capacity to do effective modeling on classical machines.
- Host: Coppersmith
Tuesday, January 27th, 2015
- No events scheduled
Wednesday, January 28th, 2015
- Faculty Candidate Seminar
- Quantum control of atoms, ions, and nuclei
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin Hall
- Speaker: Christian Schneider, UCLA
- Abstract: Cold atoms and ions provide an interesting playground for a
variety of measurements of fundamental physics. Using RF traps, experiments
become possible with both large ensembles of ions, e.g. in cold chemistry, and
few/single ions, such as in quantum computations/simulations or optical clocks,
where ultimate quantum control is required. In the first part of the talk,
recent results from our work on cold chemistry and cold molecular ions using a
hybrid atom--ion experiment will be presented. We have developed an integrated
time-of-flight mass spectrometer, which allows for the analysis of the complete
ion ensemble with isotopic resolution. Using this new setup, we have
significantly enhanced previous studies of cold reactions in our
system. Potential routes towards ultra-cold reactions at the quantum level
will be presented. Current work aims at demonstrating rotational cooling of
molecular ions and photo-associating molecular ions.
The second part of the talk reports on our results of the search for the
low-energy isomeric transition in thorium-229. This transition in the
vacuum-ultraviolet regime (around 7.8 eV) has a lifetime of tens of
minutes to several hours and is better isolated from the environment
than electronic transitions. This makes it a very promising
candidate for future precision experiments, such as a nuclear clock or tests of
variation of fundamental constants, which could outperform implementations
based on electronic transitions. Our approach of a direct search for the
nuclear transition uses thorium-doped crystals and, in a first experiment,
synchrotron radiation (ALS, LBNL) to drive this transition. We were able to
exclude a large region of possible transition frequencies and lifetimes.
Currently, we continue our efforts with enhanced sensitivity using a pulsed VUV
laser system.
- Host: Coppersmith
Thursday, January 29th, 2015
- Faculty Candidate Seminar
- Noise in superconducting circuits: microscopic theory and open questions
- Time: 4:00 pm - 5:00 pm
- Place: 4274 Chamberlin
- Speaker: Lara Faoro, Laboratoire de Physique Theorique et Hautes Energies
- Abstract: I review the main sources of noise in superconducting circuits: charge noise, critical current noise, quasiparticle poisoning and flux noise. I discuss the microscopic mechanism for these noises and show that charge and critical current noise are accounted for by the microscopic model that assumes the presence of localized electron states at the Superconductor Insulator interfaces. Due to the large electron electron interaction these states form resonances close to the Fermi surface. These states serve as traps where the quasiparticles live for a long time. The spins of the quasiparticles in these states produce flux noise of the right magnitude and frequency dependence. However the correlation between the magnetization and susceptibility noise observed by R. McDermott remains unexplained.
- Host: Coppersmith
Friday, January 30th, 2015
- No events scheduled