Researchers and students from the Faculty of Physics at the University of Warsaw, in collaboration with the QOT Center for Quantum Optical Technologies, have achieved a groundbreaking feat by developing an innovative method for performing the fractional Fourier Transform of optical pulses using quantum memory. This remarkable achievement marks the first experimental implementation of such a transformation in this type of system, placing the team at the forefront of global research in this field.
Published in the esteemed journal Physical Review Letters, the research conducted by the students involved testing the implementation of the fractional Fourier Transform using a “Schrödinger’s cat” state, which involves a double optical pulse. The Fourier Transform is a fundamental operation that links the time and frequency characteristics of waves, allowing the description of a wave in either domain. The fractional Fourier Transform extends this concept by enabling a partial transition from a time-based wave description to a frequency-based one, resembling a rotation of the wave’s distribution in the time-frequency domain.
This innovative transformation has immense practical applications, particularly in the development of spectral-temporal filters for noise elimination and the creation of algorithms that leverage the quantum properties of light to precisely differentiate pulses of different frequencies. Its significance is most pronounced in fields such as spectroscopy, which explores the chemical properties of matter, and telecommunications, where the transmission and processing of high-precision and high-speed information are crucial.
The researchers utilized a quantum memory, equipped with quantum light processing capabilities, based on a cloud of rubidium atoms held in a magneto-optical trap. By subjecting the pulse to time and frequency lenses during the storage and reading processes, the team harnessed the power of quadratic phases to process the signal effectively. The memory, placed in a varying magnetic field, enabled the storage of components with different frequencies in different regions of the atom cloud. Despite the fragility of double pulses, which are prone to decoherence, the team successfully executed faithful operations in these delicate states.
While further mapping of the method to other wavelengths and parameter ranges is necessary before its direct application in telecommunications, the fractional Fourier Transform holds immense promise for advanced optical receivers in cutting-edge networks, including optical satellite links. The quantum light processor developed at the University of Warsaw empowers efficient exploration and testing of new protocols in this field.
This groundbreaking achievement by the research students and their collaboration with the QOT Center opens up new possibilities in the realm of quantum optical technologies. Their innovative approach to implementing the fractional Fourier Transform using quantum memory not only expands our understanding of quantum physics but also paves the way for transformative advancements in telecommunications and other fields where precise manipulation of light is paramount.