Controllable optical phase shift over one radian from a single isolated atom

Abstract

Fundamental optics such as lenses and prisms work by applying phase shifts to incoming light via the refractive index. In these macroscopic devices, many particles each contribute a miniscule phase shift, working together to impose a total phase shift of many radians. In principle, even a single isolated particle can apply a radian-level phase shift, but observing this phenomenon has proven challenging. We have used a single trapped atomic ion to induce and measure a large optical phase shift of $1.3\pm 0.1$ radians in light scattered by the atom. Spatial interferometry between the scattered light and unscattered illumination light enables us to isolate the phase shift in the scattered component. The phase shift achieves the maximum value allowed by atomic theory over the accessible range of laser frequencies, validating the microscopic model that underpins the macroscopic phenomenon of the refractive index. Single-atom phase shifts of this magnitude open up new quantum information protocols, including long-range quantum phase-shift-keying cryptography [1,2] and quantum nondemolition measurement [3,4].

submitted

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Cited by in corpus (6)

• Antiresonance phase shift in strongly coupled cavity QED
• Cascaded two-photon nonlinearity in a one-dimensional waveguide with multiple two-level emitters
• Propagation of light through small clouds of cold interacting atoms
• Site-resolved imaging of single atoms with a Faraday quantum gas microscope
• The phase shift induced by a single atom in free space
• Ultralong Faraday laser as an optical frequency standard