Colloquium

IQC Colloquium Featuring Anupam Mazumdar, University of Groningen

We are led to create a massive and large spatial quantum superposition to probe the quantum nature of gravity in a laboratory. In particular, to witness the quantum entanglement mediated via the quantum nature of gravity, we will need to prepare a pure quantum state of mass 10^{-15} -10^{-14}Kg with a spatial quantum superposition of 10-100 microns and a coherence time of nearly 1-2 seconds. ...

IQC Colloquium featuring Professor Jaewan Kim, Professor/Vice-President of Korea Institute for Advanced Study (KIAS), President of Quantum Information Society of Korea (QisK)

A coherent state can be interpreted as a superposition of pseudo-number states with equal weight. Using cross-Kerr nonlinearity two coherent states can be made into a maximal entanglement of pseudo-number states and pseudo-phase states. Some applications of the entanglements of pseudo-number/phase states, such as quDit teleportations, will be discussed.

Jonathan Lavoie, Experimental Physicist, Xanadu Quantum Technologies

A quantum computer attains computational advantage when outperforming the best classical computers running the best-known algorithms on well-defined tasks. No photonic machine offering programmability over all its quantum gates has demonstrated quantum computational advantage: previous machines were largely restricted to static gate sequences. I will discuss a quantum computational advantage using Borealis, the latest of Xanadu’s photonic processors offering dynamic programmability and available on the cloud. This work is a critical milestone on the path to a practical quantum computer, validating key technological features of photonics as a platform for this goal.

Previously, higher-order Hamiltonians (HoH) had been shown to offer an advantage in both metrology and quantum energy storage. In this work, we axiomatize a model of computation that allows us to consider such Hamiltonians for the purposes of computation. From this axiomatic model, we formally prove that an HoH-based algorithm can gain up to a quadratic speed-up (in the size of the input) over classical sequential algorithms—for any possible classical computation. We show how our axiomatic model is grounded in the same physics as that used in HoH-based quantum advantage for metrology and battery charging. Thus we argue that any advance in implementing HoH-based quantum advantage in those scenarios can be co-opted for the purpose of speeding up computation. 

QNC 1201
 

Experimental relativistic zero-knowledge proofs

In this work, we report the experimental realisation of such a zero-knowledge protocol involving two separated verifier-prover pairs. Security is enforced via the physical principle of special relativity, and no computational assumption (such as the existence of one-way functions) is required. Our implementation exclusively relies on off-the-shelf equipment and works at both short (60m) and long distances (>400m) in about one second. This demonstrates the practical potential of multi-prover zero-knowledge protocols, promising for identification tasks.

John Wright, University of Texas at Austin

The local Hamiltonian problem is one of the most fundamental problems in quantum computing. It is a natural generalization of classical constraint satisfaction problems to the quantum regime, and it is the canonical QMA-complete problem. In addition, it arises naturally in the study of many-body physics. Given an instance of the local Hamiltonian problem, the object is to find its ground state or the energy of this state.

Talk abstract:

IQC Colloquium - Chunqing Deng, Quantum Scientist and Head of the Experimental Group Alibaba Quantum Laboratory

The success of superconducting quantum computing (SQC) has so far been largely built upon the transmon qubit. Finding an alternative qubit that drastically outperforms transmon represents one of the most fundamental and exciting frontiers of SQC. The fluxonium qubit stands out as a promising candidate, due to its long coherence times and large anharmonicity. Furthermore, fluxonium can be directly integrated into the existing circuit-QED schemes for scaling.

Quantum Today is an exciting new seminar series that pulls its themes from recently published scientific articles. Join us as we sit down in conversation with researchers to talk about their work, what’s the impact and where their research will lead to.

Colloquium speaker: Anja Metelmann, Free University Berlin

Parametric couplings offers the exciting possibility to manipulate and control interactions between engineered quantum systems. Such systems are artificial mesoscopic systems whose dynamics are governed by the laws of quantum mechanics. Prominent examples of these mesoscopic systems are ultracold trapped atoms and ions, superconducting circuits and electro/optomechanical systems.