PR Applied: Characterizing and tailoring multimode SPDC

(a) The process of spontaneous parametric down-conversion (SPDC) generates a two-photon wavefunction entangled in transverse position-momentum (b) We show how to measure this wavefunction efficiently and use it to tailor high-dimensional entangled states.

We are pleased to announce the publication of ‘Characterizing and Tailoring Spatial Correlations in Multimode Parametric Down-Conversion’ in Physical Review Applied. In this article, we have developed a detailed theoretical model for the quantum state of two photons entangled in their transverse position and momentum. Our model incorporates the systems used for generating entanglement and measuring it, both of which play a significant role in what the final two-photon entangled state looks like. We introduce and demonstrate a simple and efficient method to quickly characterise the two-photon joint-transverse-momentum amplitude (JTMA) using scanned phase-only holograms. We use knowledge of the JTMA to precisely tailor discrete, high-dimensional entangled states of light in the Laguerre-Gaussian (LG) and Pixel bases. We expect our work to have wide-ranging applications in experiments on multi-mode SPDC, as well as for entanglement-based quantum technologies for communication, imaging, and computation.

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.

PRL: Genuine High-Dimensional Quantum Steering

Theory and experiment coming together to demonstrate genuine high-dimensional quantum steering.

Our new paper “Genuine High-Dimensional Quantum Steering” has been published in Physical Review Letters. Collaborating along with the Quantum Information Theory Group at the University of Geneva, we formulated simple two-setting steering inequalities, the violation of which certifies a lower bound on the dimension of entanglement in a one-sided device-independent setting.

We experimentally certified 15-dimensional steering in dimension d = 31. It is the highest dimension of entanglement ever certified in a one-sided device-independent setting, which unlocks the potential of high-dimensional entanglement in several applications such as semi-device-independent quantum information protocols. More generally, this represents an important step towards the realization of noise-robust, high-capacity quantum networks in the near future.

Welcome Suraj!

We are delighted to welcome our third PhD student Suraj Goel, who joins us from India!

Suraj has completed his B.Tech in Engineering Physics at the Indian Institute of Technology Delhi (IITD), where he has worked on structured light and quantum information. His enthusiasm towards physics and experience in electronics will be valuable to the group.

Welcome to the BBQ Lab, Suraj!