Hannover 2016 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 8: Quantum Information: Concepts and Methods II

Q 8.6: Talk

Monday, February 29, 2016, 15:45–16:00, e214

Quantum-enabled measurement of the electric field using Rydberg atoms — •Eva-Katharina Dietsche, Adrien Facon, Dorian Grosso, Serge Haroche, Jean-Michel Raimond, Michel Brune, and Sebastien Gleyzes — Laboratoire Kastler Brossel, College de France, ENS-PSL, UPMC-Sorbonne Universite, CNRS, 11 Place Marcelin Berthelot 75005 Paris, France

In the classical world there is no fundamental limit to the precision of a measurement. In quantum mechanics, however, the precision of a measurement is ultimately limited by quantum fluctuations. For instance, the direction of a large angular momentum J prepared in a coherent spin state cannot be determined with a precision better than 1/sqrt(J), the standard quantum limit (SQL) for this system. A measurement uncertainty below the SQL can only be attained by the use of quantum-enabled metrology techniques. It is then possible to reach the ultimate limit, the Heisenberg limit, which scales as 1/J.

Here, we present a quantum-enhanced measurement of the electric field using mesoscopic Schrödinger-cat-like superpositions of Rydberg states. The atom behaves like a large angular momentum J whose precession frequency depends on the electric field. Instead of performing a standard Ramsey experiment using a coherent spin state, we prepare the atom in a cat-like state and measure the quantum phase accumulated by the spin during its Ramsey evolution. With this single-atom-electrometer we succeed in measuring field variations in the order of 1mV/cm in 100ns, beating the SQL. The extreme sensitivity of this measurement could pave the way to many practical applications.