Experimental realization of quantum zeno dynamics

Abstract

It is generally impossible to probe a quantum system without disturbing it. However, it is possible to exploit the back action of quantum measurements and strong couplings to tailor and protect the coherent evolution of a quantum system. This is a profound and counterintuitive phenomenon known as quantum Zeno dynamics. Here we demonstrate quantum Zeno dynamics with a rubidium Bose–Einstein condensate in a five-level Hilbert space. We harness measurements and strong couplings to dynamically disconnect different groups of quantum states and constrain the atoms to coherently evolve inside a two-level subregion. In parallel to the foundational importance due to the realization of a dynamical superselection rule and the theory of quantum measurements, this is an important step forward in protecting and controlling quantum dynamics and, broadly speaking, quantum information processing.

Fisher information from stochastic quantum measurements

“…(12). Because of the constraint in the distribution shape variation, the two results differ by the square of the derivative of the second moment with respect to the parameter, due to the derivative chain rule…”

“…As a matter of fact, an unstable quantum system, if observed continuously, will never decay, and its evolution remains frozen. As main application, the Zeno effect has been theoretically exploited to preserve coherent dynamics in a specific subspace of the Hilbert space, by the creation of decoherence-free regions [10,11], and it has been experimentally confirmed first with a rubidium Bose-Einstein condensate in a five-level Hilbert space [12] and later in a multi-level Rydberg state structure [13].…”

Zeno Hall Effect

“…S11). Here |e can be made unstable via coupling to the 5 2 P 3/2 manifold by a resonant laser with Rabi frequency Ω r which can be tuned to control the effective loss rate [24].…”

“…Our idea is based on two key ingredients: (i) to use dissipation to tailor the accessible Hilbert space S and hence to change the effective Hamiltonian (see Fig. 1 (a)) [23][24][25]; (ii) the noncommutativity of position operators in a constrained Bloch band with a nontrivial Berry curvature [26]. (i) exploits the quantum Zeno (QZ) effect [27][28][29], which is well studied in the context of quantum measurement [30,31] and occurs also for strong dissipation [32][33][34] as a continuous limit of repeated measurements [23].…”

Heating from continuous number density measurements in optical lattices

“…While this back action can be a useful resource [6][7][8][9][10][11][12], more often it leads to unwanted heating or decoherence [13][14][15][16][17]. We consider measuring the local density of atoms in a lattice.…”