Tag: Papers

We are happy to announce our most recent arXiv submission: Equilibration of objective observables in a dynamical model of quantum measurements (https://arxiv.org/abs/2403.18016). There are many unanswered questions when it comes to quantum measurements. One such question: how can something seemingly irreversible, like a measurement, arise from unitary (and therefore reversible) dynamics? We find that the answer lies in quantum thermodynamics and the idea of equilibration-on-average!

In this paper, we work within the framework of the Measurement Equilibration Hypothesis (MEH) to construct a set of objectifying observables, best at objectively encoding the measurement statistics of a system. Our work has foundational implications for the emergence of classicality, as well as providing a step towards a fully physical model of quantum measurements. This work was carried out in collaboration with Dr. Max Lock and Dr. Tom Rivlin from the Quantum Information and Thermodynamics group (QuIT Physics) at TU Wien.

We’re very excited to share that our recent work was published in Physical Review Letters while also being highlighted on the cover of the journal!

In this collaboration with groups from University of Leeds and Imperial College London, we program high fidelity non-unitary qutrit operators inside a multi-mode fiber, simulating fusion and braiding of non-Abelian D(S₃) anyons. For this to work, we combine techniques developed in our previous works such as characterizing multi-mode fibers, designing non-unitary operations, as well as programming optical circuits.

You can read the open-access publication here:
Unveiling the Non-Abelian Statistics of D(S₃) Anyons Using a Classical Photonic Simulator, Phys. Rev. Lett. 132, 110601 (2024)

We are happy to announce that our work has been published in AVS Quantum Science. In this special edition publication, we commemorate not only the important research of the late Jonathan P. Dowling, but also his notoriously wacky sense of humour. We demonstrate two-photon entanglement in the transverse spatial mode degree of freedom, particularly where one photon carries the fundamental Gaussian mode and the other a higher order Laguerre-Gaussian mode with index (ℓ) or radial (p). Taking inspiration from Dowling’s N00N states, we call these ℓ00ℓ-entangled states (we leave it up to your imagination as to what the radial (p) states may be called) .

Using the combination of a spatial light modulator (SLM) and a single mode fibre (SMF), we can make arbitrary coherent projective measurements on our generated ℓ00ℓ states. This allows us to demonstrate a “twisted” quantum eraser where Hong-Ou-Mandel interference is recovered between two distinguishable photons by projecting them into a rotated LG superposition basis. Furthermore, we verify entanglement by using an entanglement witness and reconstructing the density matrix.  We find that our generated ℓ00ℓ states have fidelities of 95.31% and 89.80% to their respective ideal maximally entangled states.

You can read the (open-access) publication here: https://pubs.aip.org/avs/aqs/article/5/4/045004/2920276/00-entanglement-and-the-twisted-quantum-eraser

Our work was recently published in Optics Express and was highlighted as the Editor’s Pick. In this work, we present a method to fully characterize the transmission matrices of complex media using neural networks.

While similar methods existed, few of them could measure the relative phases between rows of the transmission matrix. Relative phases are necessary for coherent control of light after it propagates through given complex media, allowing their applications in optical networks, biomedical imaging, and quantum information processing.

Doing simple modifications to our setup and performing randomised measurements allows full recovery of transmission matrix using (what we call) multi-plane neural networks (MPNN). We show that our technique performs a much more accurate measurement as compared to the standard existing method of measurements on the same physical setup. Moreover, our technique is extremely robust to noise, retrieving a high-quality transmission matrix even when the measured data is majorly just noise (upto SNR =0.8)!

We also demonstrate the scalability of this method, to characterize multiple complex media simultaneously in a highly non-trivial and non-convex system.

You can read more about this work which is open access at doi.org/10.1364/OE.500529 . We have included all the codes, experimental and simulational datasets with the paper which can be found on Zenodo.

Writing in the Royal Society of Edinburgh blog, Mehul describes how shaping light in space and time can enable the internet of the future!