Scientists Have Just Found the 'Missing Piece' for the Perfect Quantum Computer

The realization of large-scale quantum computers is still distant, but it seems that a new material represents the ideal candidate to accelerate their progress. A group of scientists from the Faculty of Physics at the University of Warsaw, in collaboration with researchers from the National University of Singapore and Radboud University in the Netherlands, have observed for the first time the emission of single photons within the two-dimensional material ZnPS3 (zinc and phosphorus trisulfide).

This result represents an advancement in the study of materials destined for quantum technologies, as it demonstrates that even a two-dimensional layered crystal can function as a source of single photons, a fundamental element for applications like quantum computing and quantum cryptography. Quantum computers use qubits instead of traditional binary bits. Unlike conventional systems, qubits can simultaneously take on values between 0 and 1, a characteristic that allows for numerous calculations to be performed in parallel and to tackle problems that would take decades for current supercomputers.

One of the major obstacles to the development of these machines, however, concerns the materials used to make the qubits. Many of the technologies currently being experimented with require temperatures close to absolute zero to maintain stable quantum states, a condition that makes widespread deployment difficult. For this reason, interest is growing in van der Waals two-dimensional materials, which offer advantages over traditional color centers in diamond. These crystals can easily be transferred to different substrates and directly integrated into silicon chips, miniaturized circuits, or optical fibers, facilitating the creation of quantum processors integrated into a single device.

In the work published by the researchers, thin flakes of ZnPS3, with thicknesses in the nanometer range, were analyzed. The material possesses a bandgap of 3.63 eV, a particularly interesting technical characteristic because it requires a high amount of energy to liberate the electrons. This property allows for operation at higher voltages and temperatures, reduces energy losses at high frequencies, and makes it possible to design more compact components compared to silicon-based hardware.

During the experiments, the material was illuminated with a laser. At the location of a point defect present in the crystal lattice, a sequence of single photons characterized by high polarization appeared. This is a particularly useful property for applications dedicated to quantum communication and cryptography systems. An important part of the study involved identifying the microscopic mechanism responsible for the observed phenomenon. The hypothesis put forward by the research group suggests that the origin of the emission may be linked to the presence of vacancies of single phosphorus atoms within the crystal structure.

The discovery, therefore, expands the number of materials potentially suitable for the realization of future quantum devices and confirms the potential of two-dimensional crystals in the development of components that can be easily integrated into next-generation electronic platforms.