Seminar

Wolfgang Ketterle - MIT

The properties of ultracold atoms can be profoundly modified with the help of laser beams. They can modify the wavefunction of neutral atoms in such a way that they show behavior of charged particles, e.g. electrons in high magnetic fields. In this way, synthetic magnetic fields and spin-orbit coupling have been realized, and a supersolid phase has been observed. A supersolid is superfluid and breaks translational symmetry, i.e. it has shape.

Tian Zhang, University of Oxford

In ordinary, non-relativistic quantum theory, especially in quantum information, space and time are treated differently. For example, time is a parameter rather than an operator; states are defined across the whole space but only at one time, and then evolve under the prescribed dynamics. These go against our intuition from relativity. Thus, space-time density matrices have been introduced and here we discuss one of these formulations called pseudo-density matrix (PDM) which treats space and time indiscriminately.

IQC Colloquium - Layla Hormozi, IQC

We study the role of Hamiltonian complexity in the performance of quantum annealers. It is well-known that non-stoquastic Hamiltonians are more complex than stoquastic Hamiltonians and universal adiabatic quantum computing is possible when they are employed. Here we ask whether utilizing non-stoquastic Hamiltonians in quantum annealers can lead to a better performance in solving optimization problems.

Security Proof for Discrete-Modulated Continuous Variable Quantum Key Distribution

Speaker: Twesh Upadhyaya

Yaoyun Shi, Director, Alibaba Quantum Laboratory (AQL)

I will take this opportunity to share with the Waterloo quantum community the thinkings behind Alibaba Group's quantum computing program and our main activities. Questions and comments from the audience are welcome.

About the speaker: Yaoyun Shi is a computer scientist trained at Beijing University, Princeton, and Caltech. He taught at University of Michigan before moving to Alibaba to launch its quantum computing program.

Jinglei Zhang, Aarhus University

When a quantum system is monitored with a sequence of measurements, its evolution is given by a stochastic quantum trajectory. At any time the state, and therefore any prediction we can make about an observable, is dependent on previous measurement outcomes. Past quantum state, on the other hand, is a general theory that allows us to include the information collected about the system with later measurements.

Luca Dellantonio, University of Copenhagen, Denmark

The fields of opto- and electromechanics have facilitated numerous advances in the areas of precision measurement and sensing, ultimately driving the studies of mechanical systems into the quantum regime. To date, however, the quantization of the mechanical motion and the associated quantum jumps between phonon states remains elusive. For optomechanical systems, the coupling to the environment was shown to preclude the detection of the mechanical mode occupation, unless strong single photon optomechanical coupling is achieved.

Konrad Banaszek - Centre of New Technologies, University of Warsaw

Quantum physics holds the promise of enhanced performance in metrology and sensing by exploiting non-classical phenomena such as multiparticle interference. Specific designs for quantum-enhanced schemes need to take into account noise and imperfections present in real-life implementations.

Dmitri Iouchtchenko

It has been suggested that placing dipolar linear rotors in one-dimensional lattices at zero temperature results in a model that has a transition between ordered and disordered phases. We use the density matrix renormalization group (DMRG) to compute ground states of this model near the critical point to provide further evidence of the phase transition. In particular, we numerically demonstrate divergences in both the entanglement entropy and the correlation length.

​

Brad Lackey, University of Maryland

A nonlocal game with a synchronous correlation is the ideal protocol for quantum key distribution. In this work we examine analogues of Bell's inequalities for synchronous correlations. We show that unlike in the nonsynchronous case (e.g. with the CHSH inequality) there can be no quantum Bell violation among synchronous correlations with two measurement settings. However we exhibit explicit analogues of Bell's inequalities for synchronous correlation with three measurement settings and two outputs that do admit quantum violations.