When Atoms and Chips Meet: Quantum Technology Outside the Lab

It was during an undergraduate project at the Hebrew University when Dr. Roy Zektzer first learned of the world of optical chips, and got hooked. “The ability to control the movement of light on a millimeter-scale chip, instead of through an optical system that takes up an entire table, fascinated me,” he says. “Ever since, I’ve been trying to take more and more capabilities from large, complex optical systems and transfer them onto a chip.”

Getting atoms to communicate with the world
Dr. Zektzer completed a master’s degree and a PhD in applied physics at the Hebrew University, specializing in nanophotonics and light-matter interaction. During his PhD studies, he focused on the interaction of atoms and molecules with nanoscale waveguides on a chip. “There’s something that continues to fascinate me about the idea of an atom moving at hundreds of meters per second, passing by a structure just hundreds of nanometers in size, and in that brief window of time, we manage to get it to interact with light in a meaningful manner,” he says. “This ability has many applications. Atoms provide us with a natural, highly accurate standard of frequency and energy, which is why they lie at the heart of technologies such as atomic clocks, sensors, and magnetometers. Combining them with on-chip photonics could dramatically miniaturize such systems, while also introducing new possibilities for quantum communication and information processing.”

After completing his PhD, Dr. Zektzer joined the Joint Quantum Institute in Maryland, a collaboration of NIST and the University of Maryland. There, he extended his work to quantum devices, particularly the interaction between single atoms and single photons, and developing the optical systems required to operate them. “Ultimately, a large part of my research deals with the question of how to get atoms to communicate with the outside world,” he explains. “Atoms operate at very specific frequencies, whereas communication systems, lasers, and photonic components sometimes operate at different frequencies. We want to build on-chip interfaces that join these two worlds.”

To accomplish this, he uses nonlinear optical processes through which one can convert light from one wavelength to another, or generate on-chip light at the frequency needed to drive the atoms. But the connection also works in the opposite direction: atoms themselves are an especially strong nonlinear optical system, and can be used to make photons affect one another. “This is the connection around which the lab is built: atoms, integrated photonics, and nonlinear and quantum optics – all on the same chip.”

The goal: a complete quantum system on a chip
After three years in Maryland, Dr. Zektzer returned to Israel and is now a faculty member in the electro-optics track of the electrical engineering program at Bar-Ilan University’s Faculty of Engineering. His Hybrid Quantum Photonics Chips Lab tackles one of the fundamental challenges of combining atoms and photonics: atoms move very fast, while the optical fields on the chip are very small. “Atoms move at a typical speed of about 300 meters per second, while the optical mode they need to interact with can be as small as a single micron,” he explains. “So we’re working in two complementary directions: on one hand, we’re developing structures that extend the interaction time and preserve the atoms’ coherence; on the other hand, we’re learning to utilize very short interactions to perform fast quantum operations.”

The vision isn’t just to miniaturize a single component, but to build a complete, integrated quantum system. “In the end, I don’t want the chip to be a small component connected to a giant system on an optical table. The goal is to miniaturize both the quantum function itself and the systems that operate it – the light sources, the interfaces, and the optical processing.”

A significant advantage of this approach is that our research focuses on hot atomic systems, which can operate without cooling the atoms to near-absolute zero temperatures. “The goal is to reach a small, stable chip that operates at room temperature that will ultimately be able to work outside the lab as well.”

From quantum memories to atomic sensors
Research at the lab incorporates several complementary fields. One of these is the development of quantum information processing devices that operate via atom-photon interactions: quantum memories, single-photon sources, and quantum gates. Part of the research explores interactions with a collection of atoms in special waveguides, and another part attempts to reach the extreme regime in which a single atom interacts strongly with a single photon inside a tiny optical cavity on the chip.

Another direction covers metrology and sensing. Atoms act as a natural, highly precise “ruler,” and the aim is to harness them on a chip to measure time and frequency, electromagnetic fields, and other physical quantities. In the future, such systems could be used in compact sensors, atomic clocks, and precision measurement systems.

The lab is also developing light sources and nonlinear on-chip optical processes. “An atomic system sometimes requires several lasers at different wavelengths. If you want the technology to be useful, you can’t rely on a table full of lasers and optical components,” says Dr. Zektzer. “That’s why we want to generate both the light sources and the frequency conversions on the chip itself.”

The same processes can also connect quantum systems with communication networks. A photon created in a wavelength that suits an atom is not necessarily suited for efficient long-distance transmission via optical fibers. Quantum frequency conversion can, for example, take a photon generated in an atomic system and transform it into the wavelength range suitable for quantum communication while preserving the quantum information it carries.

Taking quantum technology outside the lab
In recent years, quantum technology has been gradually moving from basic research to systems with real-world applications. Quantum key distribution (QKD) has already been demonstrated in communication networks and is used in commercial systems, while quantum sensing and meteorology offer potential applications in navigation, communications, medicine, and security.

But for such technologies to become widespread, showing that the physics works is simply not enough. “Many of the best quantum systems today are still large, complex systems confined to laboratories,” says Dr. Zektzer. “The challenge I'm interested in is taking the amazing physics we’ve already learned to execute and turning it into something that's small, stable, and integrable.”

According to him, this is part of a much broader shift in the world of technology. “The amount of information we transmit and process keeps growing, and integrated photonics is becoming an important part of our technological infrastructure. At the same time, we’re learning to control quantum systems at a level that was not possible before. The connection between these two things – integrated photonics and atomic and quantum systems – can open up possibilities we’re only just starting to understand.”

In search of the next generation of researchers
Dr. Zektzer is currently expanding his team and recruiting master's and doctoral students, postdoctoral researchers, and a lab manager. "Research in our lab has the advantage of being accessible from different fields," he says. "You might be interested in atomic physics, quantum optics, nanophotonics, chip design, nanofabrication, or nonlinear optics – at the end of the day, the projects in our lab connect all these fields."

For Dr. Zektzer, this connection is also what makes the current era especially exciting. “We’re at a point where ideas that once required an entire lab can now be imagined on a chip. I hope our research will help turn light-matter interactions into a foundation for practical quantum systems such as communication, sensing, precise measurements, and information processing,” he states, adding that "whoever joins us now will have the opportunity to be part of this process from the ground floor.”

Sounds interesting?

For more information and to join the lab, please contact Dr. Roy Zektzer: roy.zektzer@biu.ac.il