Could metasurfaces be the following quantum data processors?

Key takeaways

• New analysis reveals that metasurfaces may very well be used as sturdy linear quantum optical networks
• This method may eradicate the necessity for waveguides and different typical optical elements
• Graph concept is useful for designing the functionalities of quantum optical networks right into a single metasurface

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In the race towards sensible quantum computer systems and networks, photons — elementary particles of sunshine — maintain intriguing potentialities as quick carriers of knowledge at room temperature. Photons are usually managed and coaxed into quantum states through waveguides on prolonged microchips, or by way of cumbersome gadgets constructed from lenses, mirrors, and beam splitters. The photons develop into entangled – enabling them to encode and course of quantum data in parallel – by way of complicated networks of those optical elements. But such programs are notoriously troublesome to scale up because of the giant numbers and imperfections of elements required to do any significant computation or networking.

Could all these optical elements may very well be collapsed right into a single, flat, ultra-thin array of subwavelength components that management gentle in the very same manner, however with far fewer fabricated elements?

Optics researchers within the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) did simply that. The analysis crew led by Federico Capasso, the Robert L. Wallace Professor of Applied Physics and Vinton Hayes Senior Research Fellow in Electrical Engineering, created specifically designed metasurfaces — flat gadgets etched with nanoscale light-manipulating patterns —  to behave as ultra-thin upgrades for quantum-optical chips and setups.

The analysis was printed in Science and funded by the Air Force Office of Scientific Research (AFOSR).

Capasso and his crew confirmed {that a} metasurface can create complicated, entangled states of photons to hold out quantum operations – like these executed with bigger optical gadgets with many various elements.

“We’re introducing a major technological advantage when it comes to solving the scalability problem,” mentioned graduate scholar and first creator Kerolos M.A. Yousef. “Now we can miniaturize an entire optical setup into a single metasurface that is very stable and robust.”

Metasurfaces: Robust and scalable quantum photonics processors

Their outcomes trace at the potential of paradigm-shifting optical quantum gadgets primarily based not on typical, difficult-to-scale elements like waveguides and beam splitters, and even prolonged optical microchips, however as a substitute on error-resistant metasurfaces that supply a bunch of benefits: designs that don’t require intricate alignments, robustness to perturbations, cost-effectiveness, simplicity of fabrication, and low optical loss. Broadly talking, the work embodies metasurface-based quantum optics which, past carving a path towards room-temperature quantum computer systems and networks, may additionally profit quantum sensing or supply “lab-on-a-chip” capabilities for elementary science

Designing a single metasurface that may finely management properties like brightness, part, and polarization introduced distinctive challenges due to the mathematical complexity that arises as soon as the variety of photons and due to this fact the variety of qubits begins to extend. Every further photon introduces many new interference pathways, which in a traditional setup would require a quickly rising variety of beam splitters and output ports.

Graph concept for metasurface design

To carry order to the complexity, the researchers leaned on a department of arithmetic known as graph concept, which makes use of factors and features to signify connections and relationships. By representing entangled photon states as many linked strains and factors, they have been capable of visually decide how photons intervene with one another, and to foretell their results in experiments. Graph concept can be utilized in sure kinds of quantum computing and quantum error correction however is just not usually thought-about within the context of metasurfaces, together with their design and operation.

The ensuing paper was a collaboration with the lab of Marko Lončar, whose crew makes a speciality of quantum optics and built-in photonics and offered wanted experience and gear.

“I’m excited about this approach, because it could efficiently scale optical quantum computers and networks — which has long been their biggest challenge compared to other platforms like superconductors or atoms,” mentioned analysis scientist Neal Sinclair. “It also offers fresh insight into the understanding, design, and application of metasurfaces, especially for generating and controlling quantum light. With the graph approach, in a way, metasurface design and the optical quantum state become two sides of the same coin.”

The analysis acquired help from federal sources together with the AFOSR beneath award No. FA9550-21-1-0312. The work was carried out on the Harvard University Center for Nanoscale Systems, which is supported beneath National Science Foundation award No. ECCS-2025158.