arXiv: Programming quantum circuits in a complex medium

Experimental setup and results for a five-dimensional discrete Fourier gate

In a recent paper on the arXiv, we show how high-dimensional quantum optical circuits can be programmed inside a commercial multi-mode fibre through the use of inverse-design techniques. Using these methods, we were able to demonstrate the transport, manipulation, and measurement of high-dimensional photonic entanglement by using the transmission channel itself!

We also present numerical results on the scalability of our approach, showing how the resource of a high-dimensional mode-mixer allows perfect and lossless circuits to be realised in principle. By harnessing something as simple as light scattering inside a multi-mode fibre, our work serves as a new, yet practical alternative to integrated photonic platforms.

This work was done in collaboration with our QuantERA project partners Claudio Conti (La Sapienza, Rome) and Pepijn Pinkse (Uni Twente, Netherlands). We look forward to many more exciting collaborations in the future!

Congratulations Natalia!

We are very proud to announce a major achievement of our PhD student Natalia Herrera. She won the 2nd-year prize and the best talk award at the annual Postgraduate Research Conference in the School of Engineering and Physical Sciences at Heriot-Watt University. This acknowledges the fantastic talks she gives to a wide range of audiences and her passion to share her expertise.


Natalia has made outstanding achievements in the lab during her PhD as is shown by her latest Nature Physics paper titled “Unscrambling entanglement through a complex medium.” Our proud winner felt very honoured by taking home two prizes and will spend the prize money on time with her friends and family in 2022.

arXiv: Noise-robust and loss-tolerant quantum steering with qudits

Our new quantum steering protocol for single-detectors brings us a step closer towards secure one-sided device-independent quantum communication over realistic channels.

In our latest work on arXiv, we experimentally demonstrate detection-loophole-free quantum steering with qudits under extreme conditions of loss and noise. This work was done in collaboration with the Quantum Information Theory Group at the University of Geneva.

We showcase the improvements over qubit-based systems by experimentally demonstrating detection loophole-free quantum steering in 53 dimensions through simultaneous loss and noise conditions corresponding to 14.2 dB loss equivalent to 79 km of telecommunication fibre and 36% of white noise. We further show how the use of high dimensions counter-intuitively leads to a dramatic reduction in total measurement time. Our work demonstrates that qudit-entanglement can transcend the limits imposed by a realistic and noisy environment, proving itself a critical ingredient for making device-independent quantum communication over long distances a reality.

Welcome Dr. Sabine Wollmann

We are delighted to welcome our new postdoctoral researcher and Marie Sklodowska-Curie Fellow Dr. Sabine Wollmann to BBQLabs!

Sabine completed her PhD at Griffith University with Prof. Geoff Pryde and Prof. Howard Wiseman, and has worked in the groups of Prof. Hubert Krenner at University of Augsburg, Prof. Christian Kurtsiefer in Singapore, and most recently at the Quantum Engineering Technology Labs at University of Bristol.
Sabine will be an invaluable member of the team with her wealth of expertise in quantum optics and quantum information, and particularly EPR steering.

Her prestigous Marie Sklodowska-Curie fellowship – Quantum Information in Quantum Imaging – will bring exciting new directions to the group and perfectly complement the research of the team.

Sabine already out enjoying the beautiful campus at Heriot-Watt University.

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 .