Events

Superconducting Resonator with Composite Film for Quantum Information

Edward Tang, IQC

The full manipulation of a quantum system can endow us with the power of computing in exponentially increased state space without exponential growth of physical resources. In this thesis, we are dedicated to the developments in superconducting devices and layout design for their future applications in large-scale quantum computation.

Existence and Uniqueness in the Quantum Marginal Problem

Joel Klassen, IQC

The quantum marginal problem asks whether a family of quantum marginals are compatible with a global quantum state. It is of central importance to a wide range of topics in both quantum many body physics and quantum information. Often it can be the case that when a family of quantum marginals are compatible with a global quantum state, that global state is unique.

Simulation of III-V Nanowires for Infrared Photodetection

Khalifa M. Azizur-Rahman, McMaster University

The absorptance in vertical nanowire (nw) arrays is typically dominated by three optical phenomena: radial mode resonances, near-field evanescent wave coupling, and Fabry–Perot (F-P) mode resonances. The contribution of these optical phenomena to GaAs, InP and InAs nw absorptance was simulated using the finite element method. The study compared the absorptance between finite and semi-infinite nws with varying geometrical parameters, including the nw diameter (D), array period (P), and nw length (L).

Sequential measurements, disturbance and property testing

Aram Harrow, Massachusetts Institute of Technology

We describe two procedures which, given access to one copy of a quantum state and a sequence of two-outcome measurements, can distinguish between the case that at least one of the measurements accepts the state with high probability, and the case that all of the measurements have low probability of acceptance.

Chernoff Bound for Quantum Operations is Faithful

Nengkun Yu, Tsinghua University & University of Technology, Sydney

We consider the problem of testing two quantum hypotheses of quantum operations in the setting of many uses where an arbitrary prior distribution is given. The concept of the Chernoff bound for quantum operations is investigated to track the minimal average probability of error of discriminating two quantum operations asymptotically.

Mode-selection, purification, and ultrafast manipulation of quantum light with nonlinear waveguide devices

John Donohue, University of Paderborn

The temporal structure of quantum light offers an intrinsically high-dimensional and robust platform for encoding quantum information. In particular, the time-frequency degree of freedom can be explored in the frame of pulsed temporal modes, the ultrafast analogy to spatial Hermite-Gauss or orbital angular momentum modes. These overlapping temporal modes are naturally compatible with waveguide devices and fibre infrastructure, but present unique challenges to fully explore and exploit.

Scaling up single-atom spin qubits in silicon

Andrea Morello, Centre for Quantum Computation & Communication Technology, University of New South Wales

The modern information era is built on silicon nanoelectronic devices. The future quantum information era might be built on silicon too, if we succeed in controlling the interactions between individual spins hosted in silicon nanostructures.

Spins in silicon constitute excellent solid-state qubits, because of the weak spin-orbit coupling and the possibility to remove nuclear spins from the environment through 28Si isotopic enrichment.

Complexity of quantum impurity models

Sergey Bravyi, IBM Research

I will discuss classical and quantum algorithms for simulation of quantum impurity models. Such models describe a bath of free fermions coupled to a small interacting subsystem called an impurity. Hamiltonians of this form were famously studied by Anderson, Kondo, Wilson and others in 1960s.

Constraint Propagation Games

Zhengfeng Ji, University of Technology, Sydney

Constraint propagation games are simple extended nonlocal games that are motivated by the propagation checking of quantum computation and have found powerful applications in the study of quantum proof systems recently. In this talk, we will introduce their definitions and basic properties, demonstrate their uses in larger games as building blocks, and illustrate the method that turns them into nonlocal games.

Characterizing drift qubits

Timothy Proctor, Sandia National Laboratories

It is essential to benchmark and characterize real-world qubits in order to understand whether they are of sufficient quality for quantum information tasks, and if they are not, so that they can be debugged. Many techniques are designed for qubits that stay constant in time, but in reality almost all qubits suffer from some form of time-dependence.