Synopsis: Squeezed Photons Up-Converted to Higher Frequency

A new experiment uses nonlinear optics to convert a faint source of correlated photons to higher frequency, conserving their “squeezed” quantum state in the process.
Synopsis figure
Roman Schnabel/Albert Einstein Institute, Germany

Nonlinear optics can boost the frequency of incoming light but, typically, only when that light is intense. Now, for the first time, a group has demonstrated the up-conversion of a faint source of photons in a quantum “squeezed” state. In Physical Review Letters, the authors report that the high-frequency output beam largely preserves the initial quantum correlations between photon pairs, making the technique of potential interest to quantum metrology and quantum communication.

Frequency up-conversion has the potential to improve spatial resolution in imaging and photolithography, both of which are limited by the wavelength of light. The most common technique is frequency doubling, in which two photons from the same source combine in a nonlinear crystal to produce a photon with twice the frequency. Quantum states can be up-converted in this way as well, as long as the source is bright. Many quantum applications, however, require less light to avoid scattering effects.

Roman Schnabel from the Albert Einstein Institute, Germany, and his colleagues have succeeded in quantum up-conversion of a faint source, which in this case consisted of squeezed vacuum states. The squeezing, here, refers to the reduced shot noise (or number fluctuations) in a beam of correlated pairs of infrared photons (1550 nanometers). This squeezed beam combines with a pump beam (810 nanometers) in a mirror cavity containing a nonlinear crystal. Thanks to the high intensity of the pump, squeezed and pump photons interact to generate photons whose frequency is the sum of the combination (giving a visible wavelength of 532 nanometers). The researchers verified that the output light was squeezed, although less than the input. This method of up-conversion could benefit quantum information networks that need to transform infrared light in optical fibers into visible wavelengths for storage. – Michael Schirber


Announcements

More Announcements »

Subject Areas

Quantum InformationOptics

Previous Synopsis

Quantum Information

Cyberattack by Breaking and Entering

Read More »

Next Synopsis

Biological Physics

Live Cell Imaging

Read More »

Related Articles

Viewpoint: Ionization Delays That Stand Out
Optics

Viewpoint: Ionization Delays That Stand Out

Attosecond-resolution experiments have determined the delay in an electron’s emission from a molecule after being ionized with light. Read More »

Viewpoint: Liquid Light with a Whirl
Magnetism

Viewpoint: Liquid Light with a Whirl

An elliptical light beam in a nonlinear optical medium pumped by “twisted light” can rotate like an electron around a magnetic field. Read More »

Synopsis: Making Hard Problems for Quantum Computers
Quantum Information

Synopsis: Making Hard Problems for Quantum Computers

Researchers have developed a computer algorithm that doesn’t solve problems but instead creates them for the purpose of evaluating quantum computers. Read More »

More Articles