Nanomechanical Router Could Open Way for Scalable Quantum Networks

University of Copenhagen researchers have developed a nanocomponent, called a nanomechanical router, that emits quantum information carried by photons and routes the photons in different directions inside a photonic chip. The microscopic-size component could provide a way to scale up quantum technology.

The router is based on two coupled waveguides whose distance is adjusted on demand by an external voltage. The researchers showed controllable two-port routing of single photons emitted from quantum dots embedded in the same chip. They observed a maximum splitting ratio >23 decibels (dB), a low insertion loss of 0.67 dB, and a response time below 1 microsecond (μs).

A new component, called a nanomechanical router, emits quantum information carried by photons and routes the photons into different directions inside a photonic chip. Courtesy of Ola Jakup.

The work merges two research disciplines — nano-optomechanics and quantum optics — to develop an approach to photon routing that can be implemented for many material systems, wavelengths, and temperatures, including for active photonic chips containing quantum emitters. The size of the component, one-tenth the width of a human hair, makes it promising for scaling up applications.

“Bringing the worlds of nanomechanics and quantum photonics together is a way to scale up quantum technology,” said professor Leonardo Midolo. “Until now, we have been able to send off individual photons. However, to do more advanced things with quantum physics, we will need to scale systems up. ...To build a quantum computer or quantum internet, you don’t just need one photon at a time, you need lots of photons simultaneously that you can connect to each another.”

Research team from (l) to (r): Camille Papon, Leonardo Midolo, and Xiaoyan Zhou. Courtesy of Ola Jakub.

To build a quantum computer or a quantum internet, many nanomechanical routers will need to be integrated in the same chip. About 50 photons will be required to provide enough power to achieve what is known as “quantum supremacy.” According to Midolo, the new nanomechanical router makes “quantum supremacy” a realistic goal. “We have calculated that our nanomechanical router can already be scaled up to 10 photons, and with further enhancements, it should be able to achieve the 50 photons,” he said.

The invention is also an advance in technology for controlling light in a chip. Existing technology allows for only a few routers to be integrated on a single chip due to the large device footprint. The nanomechanical routers, in contrast, are so small that several thousands can be integrated in the same chip.

“Our component is extremely efficient,” Midolo said. “It is all about being able to emit as many photons at once, without losing any of them. No other current technique allows for this.”

The research was published in Optica, a publication of OSA, The Optical Society (https://doi.org/10.1364/OPTICA.6.000524).