Juan Miguel Arrazola of the Department of Physics and Astronomy will be defending his thesis:
Practical Quantum Communication
Juan Miguel is supervised by Professor Norbert Lütkenhaus.
The act of observation has profound consequences on a quantum system. I will describe our experimental demonstration of a Heisenberg microscope based on nondestructive imaging of a lattice gas. We show that the act of imaging these atoms induces their localization - a manifestation of the quantum Zeno effect.
We will review known results about order isomorphisms of C*-algebras,
and will describe some applications to complete positivity of maps and
a generalization of the Choi matrix. (This is joint work with Vern Paulsen.)
Then we will describe some applications to quantum information theory.
A classical current in a conductor radiates a classical electromagnetic field. We explore some properties of the field radiated by a conductor when electron transport must be described by quantum mechanics, i.e. when the electron current becomes quantum itself.
The dihedral coset problem (DCP) is an important open problem in quantum algorithms and has been studied since the early days of quantum computing. This problem attracts attention even from experts in cryptography due to its application to the lattice-based cryptosystems. It has been shown by Oded Regev in 2005 that the DCP has deep connections to the unique shortest vector problem and the random subset sum problem.
We report a quantum hacking strategy on a Continuous-Variable (CV) Quantum Key Distribution (QKD) system by inserting an external light. In the implementations of CV QKD systems, transmitting openly local oscillator pulses is a potential vulnerability for an eavesdropper to launch side channel attacks. In this work, other than targeting on local oscillator, we concern two imperfections in a balanced homodyne detector used in CV QKD system: the imbalance in the beam splitter and the finite linear detection limit.
The first part of the talk presents recent progress in the search for condensed matter systems hosting Majorana bound state in semiconductor-superconductor nanowire-based heterostructures. In the second part a proposal for the next steps towards manipulation of quantum information stored in topological qubits is presented.
It is a fundamental problem to decide how many copies of an unknown mixed quantum state are necessary and sufficient to determine the state. Previously, it was known only that estimating states to error ϵ in trace distance required O(dr2/ϵ2) copies for a d-dimensional density matrix of rank r. Here, we give a theoretical measurement scheme (POVM) that requires O((dr/δ)ln(d/δ)) copies of ρ to error δ in infidelity, and a matching lower bound up to logarithmic factors.
Sean Walker of the Department of Chemistry will be defending his thesis:
Molecular nanomagnets for novel spintronics devices
Sean is supervised by Professor Jonathan Baugh.
The classical max-flow min-cut theorem describes transport through certain idealized classical networks. We consider the quantum analog for tensor networks. By associating a tensor to each node in an integral flow network, we can also interpret it as a tensor network, and more specifically, as a linear map.