4-photon quantum states using topological edge modes

Topologically protected quantum entanglement emitters

This study was published in Nature Photonics last week. The experiments implement a topological ring resonator lattice using silicon photonics. A bright pump beam injected into opposite edges of the lattice can then generates two- and four-photon quantum states via four-wave mixing. The relative phase of the two pump beams can be used to control the degree of entanglement of the generated photons. This is to the best of my knowledge the first work to demonstrate generation of four-photon quantum states using a topological lattice.

 

What I found most surprising about this study is the author list, which includes PsiQuantum CEO Jeremy L. O’Brien under a University of Western Australia affiliation. Getting into Western Australia during the pandemic and their border closure (not even visitors from other Australian states allowed in) must have been quite a challenge!

 

Singapore Quantum Jobs

Qove Laboratory seeks postdoctoal fellows and PhD students: designing and building quantum technologies for quantum networks based on superconducting circuits, rare-earth ions, and integrated photonics. This is a newly-funded NRF Fellowship project with funding for 5 years.

Senior Research Fellow / Research Fellow positions at the School of Electrical & Electronic Engineering, Nanyang Technological University on development finite difference time domain methods for coupled electromagnetic and quantum systems. I guess this is related to the new Quantum Science & Engineering Centre announced at the end of last year.

Research Director in Quantum Computing and Quantum Communication at JPMorgan Chase’s Future Lab for Applied Research and Engineering. They are after someone with at least 12 years' relevant experience to investigate applications to finance, AI, optimization, and quantum key distribution.

PRX Quantum seeks an Associate Editor. The part-time Associate Editor is welcomed to maintain their current position–be it in academia, industry, or others, while contributing to PRX Quantum. They should also hold high standards for peer review, and be committed to building an exceptional reputation for the journal. Researchers from anywhere in the world can apply. This is a great opportunity!

arXiv highlights

Posting has been less frequent as I've been busy finishing revisions on some submitted manuscripts. Quite a few noteworthy preprints were posted this week:

 

Topogivity: A Machine-Learned Chemical Rule for Discovering Topological Materials

The authors propose a machine-learning approach for discovering new classes of topological materials. Looks interesting, but hard to say more because frustratingly all the details are delegated to supplementary materials which are not included...

Estimating the Euclidean Quantum Propagator with Deep Generative Modelling of Feynman paths

In the path integral formulation of quantum mechanics the probability amplitude of a particle transiting from state A to state B is given by summing over all possible trajectories between A and B, weighted by the action of each trajectory. While this is a theoretically elegant picture, the summation is extremely difficult to evaluate in practice due to the enormous number of possible trajectories. Here the authors show how machine learning techniques can be used to efficiently sample from those trajectories that contribute significantly to the transition amplitude.

 

Quantifying information scrambling via Classical Shadow Tomography on Programmable Quantum Simulators

By mapping evolution operators to density matrices in a higher-dimensional Hilbert space one can use shadow tomography to efficiently characterise quantum channels. Related works: arXiv:2110.02965 and arXiv:2110.03629.

Observation of wave-packet branching through an engineered conical intersection

When a Hamiltonian with two near-degenerate energy levels varies slowly in time, non-adiabatic Landau-Zener transitions between the energy eigenstates occur. A wavepacket initially in one eigenstate will end up in a superposition of the two eigenstates. A similar phenomenon plays a crucial role in certain chemical reaction dynamics and can be understood qualitatively in terms of the potential energy surfaces during the reaction. Quantum simulation of these complicated reaction dynamics is one potential near-term application of quantum processors, demonstrated here at a small scale using circuit QED.

Experimental observation of thermalisation with noncommuting charges

Macroscopic thermal states are described by conserved quantities such as the total energy or particle number. Curiously, the conserved quantities characterising certain thermal quantum states known as non-Abelian thermal states do not commute with each other and thus cannot simultaneously have well-defined values. This work reports the observation of a non-Abelian thermal state using a trapped ion quantum simulator.

 

To See a World in a Grain of Sand -- The Scientific Life of Shoucheng Zhang

Qi and Zhang's Reviews of Modern Physics article on topological insulators and superconductors was one of my first introductions to topological phases and I was shocked to hear of his passing in 2018. I enjoyed learning more about his life by reading this article.

 

ICOAM 2022 - call for abstracts

6th International Conference on Optical Angular Momentum
12–17 June 2022
Tampere University, Finland

ICOAM covers topics broadly related to the fields of structured light and singular optics. The conference was supposed to be held last year, but was postponed due to covid. The organisers are optimistic it can be held in person this year. The submission deadline for contributed abstracts is 1st March.

I did not yet have a chance to attend any conference from this series, but I've met many of the committee members at other events (SOILM13, Singular Optics, BIRS) and I'm sure they will put together a very thought-provoking and inspiring series of talks!