|Photon-shaping technique could lead to "nuclear" quantum computers. (Courtesy: iStockphoto/polygraphus)|
A way of modulating the waveforms of individual, coherent high-energy photons at room temperature has been demonstrated by researchers in the US and Russia. The advance opens the way for new quantum-optics technologies capable of extremely high-precision measurements, as well as the possibility of quantum-information systems based on nuclear processes. The new approach could also be useful for those doing fundamental research in a variety of areas, ranging from the role of quantum phenomena in biological processes to fundamental questions in quantum optics itself.
The technique was developed by Olga Kocharovskaya, Farit Vagizov and colleagues at Texas A&M University and the Kazan Federal University. Their set-up bears some similarity to a Mössbauer spectroscopy experiment. A sample of radioactive cobalt-57 decays to an excited state of iron-57, which then decays by emitting a 14.4 keV "soft" gamma-ray photon. This photon can then be absorbed and re-emitted by a nearby stainless-steel foil containing iron-57. Because of the Mössbauer effect, no energy is lost in the recoil of the stainless-steel lattice and the photon is emitted at 14.4 keV with very little spectral blurring.
As the foil absorbs and re-emits the photons, it is vibrated at megahertz frequencies. By making clever use of the Doppler effect, the team is able to shape a single photon into a double pulse and even a train of ultrashort pulses. This makes it possible to use the gamma-ray photons to encode quantum information in a "time-bin qubit" – quantum bits in which information is encoded in terms of the relative arrival time of pulses.
Gamma-ray shaping could lead to 'nuclear' quantum computers