Amir Hossein Safavi-Naeini

2016 Hellman Fellow

Assistant Professor, School of Humanities and Sciences, Applied Physics
Stanford University

Project Title: Quantum Mechanical Engineering of Strong Photon-Photon Interactions

The work funded by the Hellman fellowship is focused on implementing circuits that control the propagation of light on a silicon chip. The major unresolved challenge in making quantum systems from these chips is making devices that can entangle two photons. This requires a large optical nonlinearity so that one photon can modify its state depending on the state of another photon. Unfortunately, photons interact only very weakly in silicon, where optical nonlinearities are roughly six orders of magnitude too small to allow strong photon-photon interactions. In the last few years, we have demonstrated a new class of photonic devices made from silicon that have the potential for far larger photon-photon interactions. These nanostructured ‘optomechanical’ systems are designed to trap photons in a very small volume where they exert forces on a mechanical system. Mimicking the physics of kilometer-scale laser-based gravitational wave detectors such as LIGO, these systems sense incredibly minuscule displacements and forces on a chip and exhibit quantum mechanical phenomena at temperatures greater than 10 degrees above absolute zero. Surprisingly, photonic nonlinearities can emerge and be enhanced in these devices by taking into account the mechanical dynamics of optical structures. The nanoscale nature of our devices means that a single photon can impart forces large enough to cause motion, which in turn affects the state of another photon. The less massive the mechanical system and the larger the force per photon, the greater the effective interaction between two photons in the same structure. The Hellman Faculty Scholar program will allow us to develop chip-scale devices that may come closer to demonstrating, for the first time, strong photon-photon interactions in silicon. We would use these funds to support a focused year-long effort to push the limits of nanofabrication for a new class of silicon nano-optomechanical devices that may lead to break-throughs in photon-photon interactions on a chip, which remains a central challenge in quantum information sciences.

“The support from the Hellman Fellowship is extremely valuable and timely for my group. It will allow our efforts to continue unhindered for another year.”