An artist’s impression of changing the color of single photons using an integrated phase modulator based on thin-film lithium niobate. Image: Loncar Lab/Harvard SEAS.Optical photons are ideal carriers of quantum information. But to work together in a quantum computer or network, they need to have the same color – or frequency – and bandwidth. Changing a photon’s frequency requires altering its energy, which is particularly challenging on integrated photonic chips.
Now, researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed an integrated electro-optic modulator that can efficiently change the frequency and bandwidth of single photons. This device could lead to more advanced quantum computing and quantum networks. The researchers report their advance in a paper in Light: Science & Applications.
Converting a photon from one color to another is usually done by sending the photon into a crystal with a strong laser shining through it, a process that tends to be inefficient and noisy. Phase modulation, in which the oscillation of a photon wave is accelerated or slowed down to change the photon’s frequency, offers a more efficient method, but the device required for such a process, an electro-optic phase modulator, has proven difficult to integrate on a chip.
There is one material, however, that may be uniquely suited for such an application – thin-film lithium niobate.
“In our work, we adopted a new modulator design on thin-film lithium niobate that significantly improved the device performance,” said Marko Loncar, professor of electrical engineering at SEAS and senior author of the paper. “With this integrated modulator, we achieved record-high terahertz frequency shifts of single photons.”
The team also used the same modulator as a ‘time lens’ – a magnifying glass that bends light in time instead of space – to change the spectral shape of a photon from fat to skinny.
“Our device is much more compact and energy-efficient than traditional bulk devices,” said Di Zhu, the first author of the paper. “It can be integrated with a wide range of classical and quantum devices on the same chip to realize more sophisticated quantum light control.” Zhu is a former postdoctoral fellow at SEAS and is currently a research scientist at the Agency for Science, Research and Technology (A*STAR) in Singapore.
Next, the team plans to use their device to control the frequency and bandwidth of quantum emitters for applications in quantum networks.
This story is adapted from material from Harvard SEAS, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.