Scientists From ITMO University Describe And Emulate New Quantum State Of Entangled Photons
A research team from ITMO University, with the help of their colleagues from Moscow Institute of Physics and Technology and Politecnico di Torino, has predicted a novel type of topological quantum state of two photons and proved their predictions experimentally. The method developed by the researchers relies on the analogy: instead of expensive experiments with quantum structures of two or more entangled photons, they have used resonant electric circuits that can be described by similar equations. The obtained results can be useful for the creation of optical chips and quantum computers without the need for expensive experiments. The research was supported by grants from the Russian Science Foundation and the Russian Foundation for Basic Research. The research was in Nature Communications.
Quantum capabilities
Light plays a key role in modern informational technologies: with its help, information can be transmitted over vast distances via optical fibers. Scientists anticipate the invention of optical chips and computers that process the information with the help of photons – light quanta – instead of electrons, as it is done today. This will decrease energy consumption and at the same time increase the speed of computer equipment. However, to turn these predictions into reality, fundamental and applied research of light behavior at the micro- and macroscale is needed. Worldwide physicists and engineers enthusiastically work on new ways to apply the light.
In the future, this will allow us to create a lot of fascinating devices: data transmission channels that can’t be hacked, spectroscopy systems of high precision, and quantum computers.
In the paper, scientists from ITMO University theoretically proposed a special system in the form of a chain of quantum resonators (qubits), inside which one photon freely moves along the entire circuit, and two photons of certain frequency interact and always settle on one of the edges of the chain. Quantum edge states that appear due to the interaction between photons are a brand-new feature in photonics, and in the future can be used in the development of quantum optical chips.
For these dreams to come true, it requires years of studies and lots of resources: special nanostructures are needed for experiments.
Follow the example
If conducting a precise experiment is too expensive, it may be useful to come up with a model, or an analogy, which would allow one to test certain theoretical assumptions without spending too many resources. This method is quite popular in quantum physics nowadays. In the last couple of years a series of papers about analogue emulators was published. However, their authors have managed to create classical systems that describe certain quantum aspects only approximately, and only for single photons. Until recently, no one could find the right analogy that would also be suitable for systems of two or more quantums. That’s what ITMO University physicists have accomplished.
How does it work
At first sight, the system that is used in the experiment is nothing like its quantum photonics analogue. Instead of a one-dimensional microresonator chain, the researchers have created a two-dimensional circuit board, which is a square grid of capacitors size of 15x15 cells. In the corner of each cell there is an inductor that connects it with a zero potential.
Of course, the analogy that ITMO University scientists have come up with can not entirely replace experiments with quantum systems. However, the classical structure that was developed by the team allows researchers to conduct many experiments, providing valuable information for the field of quantum photonics. The fact that the scientists from St. Petersburg managed to find such an analogy for quantum systems of many particles for the first time is very promising.
Source: ITMO University