arXiv: Introducing the collected joint-transverse-momentum-amplitude

The knowledge of the collected joint-transverse-momentum-amplitude (JTMA) allows us to choose and tailor appropriate discrete variable bases to harness high-dimensional entanglement.

In a recent article published on arXiv, we have formalised the description for a two-photon position-momentum entangled state generated through spontaneous-parametric-down-conversion, referred to as the collected joint-transverse-momentum-amplitude (JTMA). This function characterizes the bi-photon state in the momentum degree-of-freedom while incorporating the effects of both the generation and measurement systems.

In this work, we formulate a theoretical model, propose a practical and efficient method to accurately reconstruct the collected JTMA, and demonstrate our technique by implementing it on two experiments in the continuous-wave near-infrared and pulsed telecom wavelength regimes. Furthermore, we discuss how accurate knowledge of the collected JTMA enables us to generate tailored discrete-variable high-dimensional entangled states that maximise metrics relevant to quantum information processing

Check out all the details and results in our pre-print: https://arxiv.org/abs/2110.03462 .

Welcome Sophie² !

We are thrilled to welcome our newest recruits Sophie and Sophie!

Sophie E. graduated from the University of Bristol with an MSc in Mathematics. After working on projects investigating continuous variable cluster states and Gaussian boson sampling, she will be joining us for her PhD from Quantum Engineering Centre for Doctoral Training in Bristol.

Sophie L. joins us from Vienna where she did her BSc and MSc in physics at University of Vienna. She gained expertise in experimental quantum optics while working in Philip Walther’s group on blind photonic quantum computing protocols.

We are very excited to have you both here! Welcome to BBQ Lab!

Mehul wins a Royal Society of Edinburgh Medal!

BBQ Lab has a medallist!

We are very proud to share that Mehul has been awarded the Royal Society of Edinburgh Early Career Medal in the Physical, Engineering & Informatic Sciences for the session 2021-22!

He was awarded the RSE Medal for his work in pushing the boundaries of our understanding of quantum mechanics and its use in modern technologies such as quantum cryptography and communications. He was recognised as having made world-leading contributions to the understanding of high-dimensional entanglement and the development of techniques for quantum communications and cryptography that are currently adopted in labs worldwide.

Congratulations to Mehul!

Journal of Optics : Entangled ripples and twists!

Artist’s depiction of entangled Laguerre-Gaussian modes in 43 dimensions

In a recent article published in IOPscience Journal of Optics (Emerging Leaders Special Issue) we demonstrate the full-field entanglement of radial (ripples) and azimuthal (twists) Laguerre-Gaussian modes of light. While the azimuthal degree-of-freedom has attracted a lot of interest over the past two decades, the radial degree-of-freedom presents some unique challenges to experimentalists.

By carefully tuning our optical system parameters and adopting some recently developed techniques for precise spatial mode measurement, we generated and measured entanglement in a 43-dimensional radial and azimuthal LG mode space. We also studied two-photon quantum correlations between 9 LG mode groups, which are of significant interest in the field of fibre optics.

Science Advances: Quantum Conference Key Agreement

Most of us have spent an inordinate amount of time over the past year in online conference calls, which are sure to become a regular feature in our lives. Recent events such as the ransomware attacks on US energy firms have highlighted more than ever the need for information security in such electronic forms of communication.

In a collaboration with the Mostly Quantum Lab at Heriot-Watt, we demonstrated the first quantum-secure conference call between four users. Using a multi-photon entangled GHZ state distributed over fiber-optic cables with a combined length of 50km, we built a secure key between four parties and used it to share an image of the Cheshire cat. It won’t be long before the first quantum-secure Zoom call!

See the original publication in Science Advances or media coverage in the journal Nature and Physics World magazine for more details.