Researchers at the National Institute of Standards and Technology (NIST) have created a tunable superconducting circuit on a chip that can place a single microwave photon (a particle of light) in two frequencies, or colors, at the same time.

This curious “superposition,” a hallmark of the quantum world, is a chip-scale, microwave version of a common optics experiment in which a device called a beam-splitter sends a photon into either of two possible paths across a table of lasers, lenses, and mirrors. The new NIST circuit can be used to create and manipulate different quantum states, and is thus a prototype of the scientific community’s long-sought “optics table on a chip.”

The experiments also created the first microwave-based bit for linear optical quantum computing. This type of quantum computer is typically envisioned as storing information in either the path of a light beam or the polarization (i.e., orientation) of single photons. In contrast, a microwave version would store information in a photon’s frequency.

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