Tag: Papers

Nature Physics: Unscrambling Entanglement

mehulmalik
A chaotic speckle pattern that results from light being scrambled by a complex medium such as a multimode optical fibre. (Image credit: M. Malik and S. Goel)

In new work from our lab published in the journal Nature Physics, we demonstrate how high-dimensional entanglement can be transported through a complex medium consisting of a commercial multi-mode fibre supporting hundreds of spatial modes. This work was done in collaboration with Dr. Hugo Defienne from University of Glasgow.

In a quantum twist, the transmission matrix of the fibre was measured by mapping the entire matrix onto a single entangled state, which is an example of state-channel duality in quantum mechanics. Furthermore, the entanglement was regained without ever manipulating the fibre or the photon that entered it. Instead, we carefully scrambled the entangled partner that remained outside, allowing us to transport 6-dimensional entanglement through the fibre!

Popular media coverage: BBC News, Physics World, Physics Today, Heriot-Watt press release

N. H. Valencia, S. Goel, W. McCutcheon, H. Defienne, & M. Malik, Unscrambling Entanglement through a Complex Medium, Nature Physics (2020), doi: 10.1038/s41567-020-0970-1.

arXiv: Pixel Entanglement in 55 dimensions!

mehulmalik
A 97-dimensional pixel hologram used in the experiment and two-photon correlation data

In a record-breaking result from our lab, we recently demonstrated the generation and certification of photonic high-dimensional entanglement with the highest quality, fastest measurement speed, largest dimensionality, and the most “entangled bits” of information till date!

We achieved this through several breakthroughs in theory and experiment, including a cleverly designed spatial-mode basis of macro-pixels and an efficient entanglement witness developed in collaboration with our colleagues in Austria and the Czech Republic. This result demonstrates that high-dimensional entanglement can indeed break out of the confines of an optical laboratory and enable practical, high-capacity quantum communication networks in the near future.

Preprint: N. H. Valencia,  V. Srivastav, M. Pivoluska, M. Huber, N. Friis, W. McCutcheon, and M. Malik, “High-Dimensional Pixel Entanglement: Efficient Generation and Certification,” arXiv:2004.04994 (2020).

Teleportation and a bag of chips

mehulmalik
An optical microscope image of the Silicon chip used in the experiment.
Image credit: Llewellyn et al, doi: 10.1038/s41567-019-0727-x

In a recent collaboration spanning Bristol, Denmark, Austria, and China, we demonstrated the teleportation of quantum states of light across two millimetre-scale Silicon chips and the on-chip entanglement of four photons in a GHZ-entangled state. Together with the Huber group at IQOQI Vienna, our team developed efficient theoretical techniques for measuring the generated multi-photon entangled states. These results open the door towards CMOS-compatible quantum technology applications in networking and computation.

Publication: D. Llewellyn et al, “Chip-to-chip quantum teleportation and multi-photon entanglement in silicon,” Nature Physics 16, 148–153 (2020).

PRX: Entanglement beats the Noise

mehulmalik
Artist’s depiction of entanglement surviving the onslaught of noise!
(Image credit: Harald Ritsch for IQOQI Vienna)

In our new paper on “Overcoming Noise in Entanglement Distribution” co-authored with colleagues in Austria, Finland, Germany, and Canada, we demonstrate how high-dimensional entanglement in the spatio-temporal degrees of freedom allows one to tolerate large amounts of noise that would generally lead to a loss of qubit, or two-dimensional entanglement. In other words, we certified entanglement with the laboratory lights on! This works demonstrates the potential for high-dimensional quantum states to not only enable high-capacity quantum networks, but also operate in realistic environmental conditions, such as in broad daylight or alongside classical data traffic. For more information, please read this APS synopsis.

Popular media coverage: Heriot-Watt press release, Wiener Zeitung, Orf.at.
Journal reference: Ecker et al, Phys. Rev. X 9, 041042 (2019), doi: 10.1103/PhysRevX.9.041042.

arXiv: Unscrambling Entanglement through a Complex Medium

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Photonic high-dimensional entanglement in the spatial degree of freedom has recently emerged as a practical way to enhance the capacity of quantum information systems, as well as increase their robustness to noise. However, while qubit entanglement has been distributed over large distances through free-space and fibre, the transport of high-dimensional entangled states of light through highly complex media has never been demonstrated.

After many months of hard work, we achieved the transport of high-dimensional spatial-mode entanglement through a commercial multi-mode fibre for the first time. In our experiment, one photon from a bipartite spatially entangled state was sent through a two-metre piece of multi-mode fibre from Thorlabs. Interestingly, while entanglement was completely lost, the resulting “scrambled” correlations captured the behaviour of the multi-mode fibre in the form of its transmission matrix. This information allowed us to recover the entanglement by only manipulating the entangled partner photon that did not enter the fibre!

For more details, please read our preprint: N. H. Valencia, S. Goel, W. McCutcheon, H. Defienne, and M. Malik, “Unscrambling Entanglement through a Complex Medium”, arXiv:1910.04490 (2019), Link: https://arxiv.org/abs/1910.04490