Recently, researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences developed
Optical photons are ideal carriers of quantuminformation. But to work in a quantum computer or network, they must have the same color (or frequency) and bandwidth. Changing the frequency of a photon requires changing its energy, which is quite difficult for integrated photonic chips.
Converting a photon from one color to anotherusually done by sending a photon into a crystal through which a powerful laser shines, a process that tends to be inefficient and noisy. Phase modulation, in which the oscillations of a photon wave are sped up or slowed down to change the frequency of the photon, offers a more efficient method, but the device required for such a process, an electro-optical phase modulator, has proven difficult to integrate onto a chip.
As part of the new study, scientists createdmodulator design based on thin-film lithium niobate. It has significantly improved the characteristics of the device. Using a built-in modulator, scientists achieved a record high terahertz frequency shift of single photons.
Changing the color of single photons using a built-in phase modulator. Credit: Loncar Lab/Harvard SEAS
Scientists used the same modulator as a “time lens”—a magnifying glass that bends light in time rather than space. The goal is to change the spectral shape of the photon.
“Our device is much more compactand “more energy efficient than traditional ones,” explain the authors of the development. “It can be integrated with a wide range of classical and quantum devices on a single chip to realize more complex quantum light control.”
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