Quantum frequency is the rate at which all matter vibrates. It was first described by Max Planck in 1900 when he assumed that radiation (light) is emitted not continuously but in discrete packets, or “quanta.” The energy of each quantum is related to its frequency, n, by the formula E = hn, where the variable h represents a constant—now known as Planck’s constant—that relates the total energy of an electromagnetic field to its frequency.
Scientists at UNSW have made progress toward the goal of a universal quantum sensor by developing a method that makes it possible to detect arbitrary frequencies. The technique uses a quantum version of frequency mixing—an important process in electronics that allows signals to be transmitted and amplified over long distances.
The team used a periodically poled low-noise quantum frequency converter (QFC) integrated on an LNOI nanophotonic waveguide to upconvert telecom-band single photons to the visible, and demonstrated nonclassical intensity correlation between them, a key quantum property that indicates the integrity of the mixed state. This is the first time such a quantum property has been observed with a QFC chip.
They also used the QFC to link a 606 nm rare-earth-ion quantum memory and a 1550 nm nitrogen vacancy center in diamond, two critical elements for future fiber-based quantum networks. these twoCurrent quantum frequency conversion techniques only transfer a portion of the signal between systems, leading to inhomogeneous broadening that degrades antibunched photon statistics. The team’s new method eliminates this limitation, making it a valuable tool for advancing quantum communications and computing applications.