Seminar

Surface Acoustic Waves in Quantum Systems

Mats Powlowski

​Surface acoustic waves (SAWs) are acoustic phonons that travel along the surface of a material and have been used for a wide variety of purposes, from RF filters to acoustic cavities to biosensors.

Juan Xu - Nanjing University of Aeronautics and Astronautics

Quantum secret sharing (QSS) mainly deals with the splitting and distributing of an arbitrary secret among n sharers using quantum resources. While quantum secret sharing schemes often use shared entangled states, it is also possible to define a notion of quantum secret sharing without the use of entangled states.

David P. Pappas, National Institute of Standards and Technology (NIST)

A brief history and overview of the requirements to guide the research and development for high-coherence superconducting quantum circuits will be given. The main focus will be on materials development at NIST. Topics will include identifying and mitigating loss due to amorphous two-level systems at interfaces and how to scale the fabrication of small aluminum-oxide tunnel junctions. The junctions were studied with atom probe microscopy to get an understanding of where the oxidation occurs.

Alexander Grimm, Yale University

In recent years, circuit quantum electrodynamics (QED) has seen considerable efforts towards protecting quantum information from unwanted sources of decoherence through quantum error correction. Independent of the implementation, this is based on encoding a logical qubit into a stable manifold within a larger Hilbert space, whose symmetries restrict the number of independent errors and make them detectable and correctable.

The number theory of quantum information

Jon Yard, IQC

Abstract: Quantum-mechanical amplitudes and unitaries are typically expressed over the complex numbers. Because there is a continuum of complex numbers, classical computations of quantum systems generally utilize finite-precision approximations by rational numbers.

Dagmar Bruss, University of Duesseldorf

The resource theory of quantum coherence studies the off-diagonal elements of a density matrix in a distinguished basis, whereas the resource theory of purity studies all deviations from the maximally mixed state. We establish a direct connection between the two resource theories, by identifying purity as the maximal coherence, which is achievable by unitary operations. The states that saturate this maximum identify a universal family of maximally coherent mixed states.

Crystal Senko: Ion traps and multi-level quantum systems

I give an overview of trapped ion quantum information experiments and discuss prospects for implementing multi-valued quantum logic using trapped ions.

Jan Haase, Universität Ulm

Whenever one is tempted to employ a quantum system for any kind of applications, the focus usually lies on two properties setting it apart from a system described by a classical theory, namely the coherent superposition of different quantum states and entanglement between two ore more constituents forming the system.

PhD Seminar

Chunhao Wang, PhD candidate

David R. Cheriton School of Computer Science

We give a dissipative quantum search algorithm that is based on a novel dissipative query model. If there are $N$ items and $M$ of them are marked, this algorithm performs a fixed-point quantum search using $O(\sqrt{N/M}\log(1/\epsilon))$ queries with error bounded by $\epsilon$. In addition, we present a continuous-time version of this algorithm in terms of Lindblad evolution.

PhD Seminar

Chunhao Wang, PhD candidate

David R. Cheriton School of Computer Science

We present a quantum algorithm for simulating the dynamics of Hamiltonians that are not necessarily sparse. Our algorithm is based on the assumption that the entries of the Hamiltonian are stored in a data structure that allows for the efficient preparation of states that encode the rows of the Hamiltonian. We use a linear combination of quantum walks to achieve a poly-logarithmic dependence on the precision.