- Spectral Compression of Narrowband Single Photons
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Abstract:
- Quantum computing promises many benefits to society, such as better development of medicine and more optimized transport systems. Quantum computational power can be increased by connecting quantum computers, forming the quantum internet. The backbone of the quantum internet relies on transferring and distributing quantum information over a network of quantum nodes. It has been proposed that interactions between atoms and single photons can be a suitable candidate for the quantum internet, as atoms have stable quantum states, while photons can travel fast and long distances with little interaction with the environment. However, for a high rate of efficient interaction between atoms and photons, it requires the matching of the frequency spectrum of the photon to the absorption profile of the atoms. Attempts to increase efficiency have been made, by filtering photons spectrally to match their bandwidths to corresponding atomic spectral profiles, but such filtering techniques leads to losses, reducing the absorption rate of photons. The above motivates for a method to reshape the spectra of the photons, with minimal losses. In this thesis, we present our work on a successful demonstration of an in-principle lossless spectral compression performed on heralded single 795 nm photons with narrow spectral bandwidths about 3 times larger than the corresponding atomic transitions, generated through four-wave mixing in cold Rubidium-87 atoms. This spectral compression technique is done by optically dispersing the photons with a narrowband cavity, then applying a time-dependent phase, to achieve a Fourier-transform limited photon. The spectral bandwidth of the photons in our experiment was compressed by a factor of 2.6, from 20.6 MHz to less than 8 MHz, almost matching the corresponding atomic transition linewidth of 6 MHz. This better matching of photon bandwidths has the potential for more efficient photon-atom interaction.
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