QuICS seminar

The nascent field of Quantum Machine Learning has been generating a substantial buzz in the last few years. The broad theme of this field is the interplay between the disciplines of quantum information processing (QIP) and of machine learning (ML). In this talk, I will review the basic trends in this new discipline.

Quantum self-testing is a tool that can allow us to test the honesty of quantum devices without needing to have access to any trusted quantum devices.  Through classical information alone (measurement settings and outcomes, for example) we can verify that quantum devices are operating according to some specification, even if we have no information on how the devices are constructed.  Self-testing can be used to test sources, measurements, and even entire quantum computations.  In this ta

Reliable qubits are difficult to engineer.  What can we do with just a few of them?  Here are some ideas: 
 
1. Memory/dimensionality test.  An n-qubit system has 2^n dimensions---a big reason for quantum computers' exponential power!  But systems with just polynomial(n) dimensions can look like they have n qubits.  We give a test for verifying that your system really has 2^n dimensions.  
 

Quantum correlations are fundamental for quantum information protocols and for our understanding of many-body quantum physics. The detection of these correlations in these systems is challenging because it requires the estimation of an exponentially growing amount of parameters. We present methods to alleviate this problem and discuss their application to physically relevant quantum states.

This talk will be about a sub-exponential time algorithm for the Best Separable State (BSS) problem. 

We present a new scheme for quantum homomorphic encryption which is compact and allows for efficient evaluation of arbitrary polynomial-sized quantum circuits. Building on the framework of Broadbent and Jeffery [BJ15] and recent results in the area of instantaneous non-local quantum computation [Spe15], we show how to construct quantum gadgets that allow perfect correction of the errors which occur during the homomorphic evaluation of T gates on encrypted quantum data.

In this talk, I will unzip a recent progress on quantum interactive proofs---communications in quantum multi-prover interactive proofs can be exponentially compressed.

Shannon's entropy power inequality gives a lower bound on the entropy power of the sum of two independent random variables in terms of the individual entropy powers. This statement and some of its consequences are information-theoretic counterparts of certain geometric inequalities. In this talk, I will give an overview of analogous statements for bosonic quantum systems. The first concerns a certain convolution operation between two quantum states: here two independent bosonic modes combine at a beamsplitter.

In a typical post-quantum scenario, the adversary has a quantum computer at their disposal, but only gets classical access to the cryptographic scheme. Recent research has shown that, if adversaries also get quantum access (e.g., the ability to encrypt or authenticate in superposition) then they can easily break many constructions currently believed to be “quantum-secure.”

I will discuss classical algorithms for computing low-energy states 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. Impurity models also play the central role in modern material simulation algorithms based on the DMFT method. Quite recently it was suggested that DMFT simulation algorithms may benefit from quantum computers.