November 2021 - ITP-quantumseminare

Tomorrow's QIT Seminar
by Joe Renes 29 Nov '21

29 Nov '21

Hi all, Tomorrow we will hear from Eloïc Vallée, who did his masters thesis in conjunction with the Brunner group in Geneva, on "mdiQKD with assumptions on the states overlap". See below for the abstract. We'll start at 2pm on zoom: https://ethz.zoom.us/j/362994444. Best, Joe %%%%%%%% Title: mdiQKD with assumptions on the states overlap Abstract: With the upcoming generation of quantum computers, secure communications will essentially depend on quantum key distribution (QKD) algorithms. One of the most promising algorithm is the measurement-device-independent QKD (mdiQKD), first proposed by Lo, Curty and Qi in 2012. We explore a modified mdiQKD protocol with a relaxed assumption on the initial states. The assumption relies on the overlap between the states and not on the exact characterization of the states. The protocol is a tripartite prepare-and-measure based protocol. Two parties prepare states and send them to a connecting node, which performs a measurement on the joint states. And no assumption is made on the node's measurement. The protocol is therefore immune to attack on the third party. A secret key can be established by verifying the honesty of the measurement at the node through observed statistics. A positive key rate is found for different situations and demonstrates the protocol viability.

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Tomorrow's QIT Seminar --- Zhenning Liu, 2pm on Zoom
by Joe Renes 08 Nov '21

08 Nov '21

Hi all, Tomorrow Zhenning Liu will tell us about his master thesis with Andru, entitled "Depth-efficient proofs of quantumness". See below for the abstract. We start as usual at 2pm on zoom: https://ethz.zoom.us/j/362994444. Best, Joe %%%%%% Abstract: A proof of quantumness is a type of challenge-response protocol in which a classical verifier can efficiently certify the quantum advantage of an untrusted prover. That is, a quantum prover can correctly answer the verifier's challenges and be accepted, while any polynomial-time classical prover will be rejected with high probability, based on plausible computational assumptions. To answer the verifier's challenges, existing proofs of quantumness typically require the quantum prover to perform a combination of polynomial-size quantum circuits and measurements. In this project, we give two proofs of quantumness constructions in which the prover need only perform constant-depth quantum circuits (and measurements) together with log-depth classical computation. Our first construction is a generic compiler that allows us to translate all existing proofs of quantumness into constant quantum depth versions. Our second construction is based around the learning with rounding problem and yields circuits with shorter depth and requiring fewer qubits than the generic construction. In addition, the second construction also has some robustness against noise.

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Tomorrow's QIT Seminar
by Joe Renes 01 Nov '21

01 Nov '21

Hi all, Tomorrow we will hear from our guest Raffaele Salvia, from SNS in Pisa, on his recent work "The classical capacity of quantum channels and the problem of energy preservation". See below for the abstract. We start at 2pm on Zoom: https://ethz.zoom.us/j/362994444. Best, Joe %%%%%% Finding the classical capacity of quantum channels is one of the main open problems in Quantum Information Theory; it has been solved only for some special classes of channels. This long-standing problem reveals a surprising connection with the optimal output entropy problem, which arises in the theory of quantum energy storage. Through the examples of the qubit amplitude-damping channel and of continuous variable Gaussian channels, I will show how this relationship can shed new light on both of the problems.

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