Current students

Quantum Randomness Expansion - New Results

Carl Miller, University of Michigan

Is it possible to create a source of provable random numbers? An affirmative answer to this question would be highly useful in information security, where random numbers are needed to provide the keys for encryption algorithms. Bell inequality violation experiments offer hope for this problem, since the outputs of a Bell violation must be non-classical and therefore not fully predictable to an adversary. The challenge is to prove something stronger: that the outputs can be processed (extracted) to obtain uniformly random data. This leads to some complex and beautiful mathematics.

Quantum optics of strongly correlated many-body systems

Igor Mekhov, University of Oxford

We show that quantum backaction of weak measurement constitutes a novel source of competitions in many-body systems, thus leading to new phenomena. We consider a system of ultracold atoms in optical lattices trapped inside a high-Q cavity, which requires a fully quantum description of both light and matter waves. The QND measurements lead to the generation of genuinely multipartite entangled modes of the matter fields, which have analogies in quantum optics (e.g. two-mode squeezing), but are non-Gaussian.

The Relativistic Quantum Information North (RQI-N) Conference, hosted by the Institute for Quantum Computing (IQC), will bring together an interdisciplinary community of researchers at the interface of quantum information science and relativity.

Hybrid quantum systems using collective degrees of freedom in solids

Yasunobu Nakamura, The University of Tokyo

In the course of the development of superconducting qubits, we learned that we can fully control quantum states of selected collective degrees of freedom in superconducting circuits. Such collective modes, rigidly extending in a macroscopic scale, strongly couple to electromagnetic fields via their large dipole moments. Moreover, Josephson junctions bring large nonlinearity into the system without adding dissipation.

Quantum information processing with superconducting quantum circuits

Archana Kamal, Massachusetts Institute of Technology

The promise of quantum computers to solve problems intractable with their best classical counterparts has catapulted quantum information processing into a major research effort in recent years. In addition, rapidly evolving capabilities in manipulating quantum systems have provided us with new insights into the dynamics of nature at small scales. One of the primary challenges in developing any practical quantum information platform, however, is to harness quantum effects on macroscopic scales.

Catalysis of Stark-tuned Interactions between Ultracold Rydberg Atoms

Aye Lu Win, Old Dominion University

The strong long-range interaction between ultracold Rydberg atoms gives rise to a number of interesting phenomena that have been studied in recent years including resonant energy transfer collisions, many-body quantum simulations, quantum information processing, and ultracold plasmas. The dipole-dipole interaction between a pair of Rydberg atoms can result in a state-changing interaction if the energy defect for the process is small.

Nanocontacts atom-by-atom with a friction emulator

Dorian Gangloff, Massachusetts Institute of Technology

Friction is the basic, ubiquitous mechanical interaction between two surfaces that results in resistance to motion and energy dissipation. To test long-standing atomistic models of friction processes at the nanoscale, we implemented a synthetic nanofriction interface using laser cooled ions subject to the periodic potential of an optical standing wave.

Measuring Entanglement Entropy in a Many-body System

K. Rajibul Islam, MIT-Harvard Center for Ultracold Atoms

Entanglement, perhaps the most counter-intuitive feature of quantum mechanics, describes non-local correlations between quantum objects. In recent years, entanglement has emerged as a central concept in our understanding of quantum many-body physics. It allows us to characterize phases of quantum matter that cannot be distinguished by broken symmetries, such as topological states.

Estimating outcome probabilities of quantum circuits using quasiprobabilities

Hakop Pashayan, The University of Sydney

We present a method for estimating the probabilities of outcomes of a quantum circuit using Monte Carlo sampling techniques applied to a quasiprobability representation.