Photons, particles that are quantum of light, have already shown great potential for development
What is the problem?
Despite the promising results of preliminary experiments, a scientific breakthrough is needed before photonic qubits can be implemented on a large scale.For example, it is known that photons can lose energy and radiation as they move from one point to another and do not interactwith each other.
Researchers from the University of Copenhagenin Denmark, the Instituto de Física Fundamental IFF-CSIC in Spain and the Ruhr University Bochum in Germany have recently developed a strategy to overcome one of these problems, namely the lack of photon-photon interaction. Their method will ultimately help in the development of more complex quantum devices.
More than 15 years of experiments
Scientists have been working on deterministicpairing single quantum emitters (quantum dots) with single photons - more than 15 years. As a result, they developed a method based on nanophotonic waveguides.
The determinism of an object can be explainedwith the help of the doctrine of determinism (from the Latin determinare - “to limit, outline, determine”). According to him, all objects are interconnected, and all phenomena and processes are mutually determined.
Typically these devices were used fordeterministic single-photon sources and sources of multiphoton entanglement. However, it was also useful for initiating nonlinear operations with photons.
Waveguide - artificial or naturala guide channel in which a wave can propagate. The power flow that is carried by the wave is located precisely inside the channel itself. Another option is that it is concentrated in the area of space adjacent to the channel.
The concept of such operations was first shownin 2015. However, they encountered difficulties when further investigating this effect. They relate to questions of fundamental physics that underlie this complex, single-photon and nonlinear interaction.
In previous studies, scientistsdiscovered that the physics that is responsible for the nonlinear interaction of light pulses is also useful for creating photonic quantum gates and “photon sorters.”
Thus, scientists conducted the first experimentalstudy of nonlinear quantum pulses that undergo nonlinear interactions due to coupling with a deterministically coupled quantum emitter.
What have the scientists done?
In a new experiment, researchersused efficient and coherent coupling of a single quantum emitter with a nanophotonic waveguide. The goal is to enable nonlinear quantum interaction between single-photon wave packets.
A wave packet is a certain set of waves,which has different frequencies. They describe a formation with wave properties, generally limited in time and space.
To do this, scientists used one quantum dot - a nanometer-sized particle that behaves like a two-level atom. It was built into a photonic crystal waveguide.
The remarkable thing about such systems is that the communication in themis deterministic. Even one photon launched into a waveguide interacts with a quantum dot. If you send pulses that contain two or more photons, it will cause quantum correlations. This is because only one photon at a time can interact with a quantum dot. Ultimately, by controlling the duration of this quantum pulse, scientists can tune these correlations and interactions between photons.
Using their experimental method, scientistsIn essence, they were able to control a photon using a second one, which is mediated by a quantum emitter. In other words, they successfully implemented nonlinear photon-photon interaction and forced particles to “communicate.”
Where it leads?
As a result, scientists developed a method thatallows photons to effectively interact with each other through communication with quantum dots. This will help create new directions for creating photon-photon quantum gates. The discovery will also be useful for creating deterministic photon sorting devices, which are necessary, for example, for quantum repeaters.
Quantum repeaters make it possible to createentanglement at remote nodes without physically sending the entangled qubit over the entire distance. Simply put, they amplify the signal and prevent photons from fading.
The new strategy has important implications for bothresearch in the field of quantum physics and for the development of quantum technologies. For example, the method will open up new possibilities for the development of quantum optical devices, and will also allow physicists to experiment with tailored complex photonic quantum states.
What's next?
Scientists are not going to stop and planexpand the experiment. At a fundamental level, they want to gain a deeper understanding of how quantum states of light are affected by traveling through a single quantum dot. However, scientists are confident that this quantum interaction can be applied in practice.
Now physicists are trying to use nonlinearphoton-photon interaction, implemented in a recent study, to simulate the vibrational dynamics of molecules. This is possible by matching the vibrational dynamics of complex molecules with the propagation of photons in advanced photonic circuits.
Read more:
NASA revealed the origin of Haumea - the most mysterious planet in the solar system
Living organisms have made Mars uninhabitable
The liver can work for more than 100 years: scientists told how this is possible
On the cover:two photons propagating in a waveguide and interacting with a single quantum emitter. As a result, the scientists achieved photon-photon interaction, which results in correlations. Credit: Le Jeannic et al.