Seminar

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. 

Joshua Choi - University of Virginia

Metal halide perovskites (MHPs) are revolutionizing the solar cell research field - the record power conversion efficiency of MHPs based solar cells has reached 22.7%, which rivals that of silicon solar cells. What is particularly exciting about MHPs is that they can be manufactured into solar cell devices at low-costing using low temperature solution processing. Based on these attributes, MHPs have been called the “next big thing in photovoltaics” and worldwide research efforts have grown explosively.

Eric Bittner, University of Houston

Entangled photons offer an exquisite probe to correlated dynamics within a material system. In my talk I shall discuss some recent experiments and our theoretical investigations into developing an input/output scattering theory approach that connects an incoming photon Fock state to an outgoing Fock state, treating both the internal (material) and photon dynamics on a consistent footing. As proof of concept, we show how entangled photons can probe the inner workings of a model system undergoing spontaneous symmetry breaking.

Felix Leditzky, University of Colorado, Boulder

Port-based teleportation (PBT) is a variant of the well-known task of quantum teleportation in which Alice and Bob share multiple entangled states called "ports". While in the standard teleportation protocol using a single entangled state the receiver Bob has to apply a non-trivial correction unitary, in PBT he merely has to pick up the right quantum system at a port specified by the classical message he received from Alice.