A connection between two research groups at the Technion gave rise to a new scientific field: quantum metamaterials

The research, which is a breakthrough in everything related to quantum information experiments, was published today in the journal Science

Joint research by the head of the Institute for Solid State Research Prof. Moti Segev from the Faculty of Physics and Prof. Erez Hasman from the Faculty of Mechanical Engineering gave birth to a new scientific field: quantum metamaterials. The findings were published today (September 13, 2018) in a joint article by the researchers in the prestigious journal Science. Students Tomer Stav and Dekla Oren from the laboratory of Research Prof. Segev, Dr. Vladimir Kleiner and students Arkady Fireman and Elhanan Magid from Prof. Hasman's laboratory participated in the study.

The research demonstrates for the first time the possibility of applying metasurfaces in the field of quantum information and quantum computing and paves the way for many applications including completely secure encryption. This research opens the possibility for interdisciplinary collaborations and the development of systems of quantum information on a chip.

Metamaterials are engineered nanoscale structures that do not exist in nature, and one of their unique categories is the group of meta-surfaces. These are very thin artificial structures, two-dimensional for that matter, produced with innovative technologies and their purpose is to have unique interactions with light. Using optical nanometer antennas that are much smaller than the wavelength. The technology developed by Prof. Hasman in his laboratory enables the construction of very precise insulating meta-surfaces made of transparent silicon, without metals, which do not absorb light.

Optical research on metasurfaces has so far only dealt with "normal" light from a table lamp or laser device, that is, classical light (electromagnetic waves). In the current work, the Technion researchers demonstrated for the first time in history the use of metasurfaces in quantum optics (light as a stream of quantum particles called photons) and quantum information. The researchers demonstrated the use of metasurfaces to create quantum entanglement - the most essential element in quantum communication, quantum computing and quantum encryption.

"In this research, we brought the field of metamaterials into the world of quantum information," says research professor Segev, one of the founders of the Helen Diller Quantum Center for Science, Materials and Engineering. "We harness here for the first time the unique properties of metamaterials to create and control quantum light. We can now engineer the quantum properties of light by designing, manufacturing and controlling the material through which it travels. In fact, a new scientific field was born here that will enable a very significant miniaturization of quantum information systems and the development of a variety of options for manipulating the quantum light in ways that normal materials do not allow. If in the past we created such systems on large tables, now we can build them on tiny chips in which metamaterials are integrated"

According to Prof. Hasman, "The main component here is an isolated metasurface that creates the interweaving between the photons. The meta-surface must be produced from transparent materials (silicon) that do not conduct and do not absorb light, therefore it is impossible to produce it from metal. In fact, we took a surface and deformed it, that is, we caused it a spatial deformation, and thus an effective magnetic field was created that creates the required correlation, that is, the interweaving. This is a huge achievement for both teams."

The researchers demonstrated the use of metamaterials to create entanglement - a phenomenon in which two particles (photons in this case) behave as physical twins that influence each other even when the distance between them is huge. An action performed on one photon immediately affects (without a time difference) the twin photon. Quantum mechanics holds that photons exist in positive and negative spin states at the same time, but as soon as they are measured they get one state. The famous analogy is "Schrödinger's cat", presented by Nobel laureate Irving Schrödinger - an analogy in which the cat lives and dies at the same time until the moment the box in which it is found is opened.

As mentioned, the current research is based on a collaboration between two of the leading laboratories at the Technion. The researchers shone a laser beam on the non-linear crystal to create pairs of photons characterized by zero angular momentum and each characterized by a different linear polarization. Each linear polarization is a sum of right circular polarization and left circular polarization, corresponding to positive and negative spin. The system directed the pair of photons to a metasurface, and the interaction between the light and the material created an entanglement of the two photons.

In the first experiment, the researchers split the photon pairs - one through the metasurface and one through the detector. They then measured the single photon that passed through the metasurface and found that it did develop an orbital angular momentum entwined with its spin. In the second experiment, the photon pairs were transmitted through the metasurface and measured using two detectors. The researchers discovered that the spin of one of the photons in the pair became entangled with the orbital angular momentum of the other photon, and vice versa.

Compete with research groups from all over the world - and win
According to Professors Segev and Hasman, "the current study was born from the idea of ​​two of our master's students - Tomer Stav and Arkady Fireman. They came to us with an innovative and groundbreaking idea that led to new directions of research and application, for example systems of quantum information on a chip and control of quantum properties in ways that are completely impossible in ordinary materials. These young people did a great job on a short schedule. We competed against very large research groups from all over the world and managed to win."

The two students, not yet 30 years old, are old friends who simultaneously completed a bachelor's degree at the Technion - Tomer in the physics faculty's excellence program and Arkady in the optics major in the mechanical engineering faculty. At the end of their bachelor's degree, they went on to their master's degree in the laboratories of Research Prof. Segev and Prof. Hasman, respectively. During their studies for the master's degree, they conceived and conducted the present study.

The research was conducted at the Helen Diller Quantum Center for Science, Materials and Engineering at the Technion. Both research groups are affiliated with the Russell Berry Institute for Research in Nanotechnology at the Technion (RBNI) and both researchers have numerous previous publications in Science.

Research Prof. Moti Segev, recipient of the 2014 Israel Prize for Chemistry and Physics Research, is the head of the Dr. Bob Shilman Chair in the Faculty of Physics and one of the founders of the Helen Diller Quantum Center for Science, Materials and Engineering at the Technion. Research Prof. Segev is a member of the Israeli National Academy of Sciences and a member of the American Academy of Arts and Sciences.

Prof. Erez Hasman completed his doctorate at the Weizmann Institute and then worked and led development for a decade in the civil and defense industry. In 1998, he was appointed a faculty member in the Faculty of Mechanical Engineering at the Technion, founded the optical engineering major in the faculty and is currently the head of the laboratory for micro- and nano-optics and the head of the Schlesinger Chair. In 2001, his research group laid the foundations for the field of optical metasurfaces, which is currently considered one of the hottest fields in optics.

For an article in Science