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Creation of a six-atom Schrödinger cat state



Dietrich G. Leibfried, Emanuel H. Knill, Signe Seidelin, Joseph W. Britton, Brad R. Blakestad, J Chiaverini, David Hume, Wayne M. Itano, John D. Jost, C. Langer, R Ozeri, Rainer Reichle, David J. Wineland


Among highly entangled states of multiple quantum systems, Schrödinger cat states are particularly useful. Cat states are equal superpositions of two maximally different quantum states. They are a fundamental resource in fault-tolerant quantum computing and quantum communication, where they can enable protocols such as open-destination teleportation and secret sharing. They play a role in fundamental tests of quantum mechanics and enable improved signal-to-noise ratios in interferometry. Cat states are very sensitive to decoherence, and as a result their preparation is challenging and can serve as a demonstration of good quantum control. Here we report the creation of cat states of up to 6 atomic qubits. Each qubits state space is defined by two hyperfine ground states of a beryllium ion, with the cat state corresponding to an entangled equal superposition of all atoms in one hyperfine state and all atoms in another hyperfine state. In our experiments the cat states are prepared in a three step process, irrespective of the number of entangled atoms. The method used to create the 4-qubit cat state also demonstrates a universal quantum logic gate for decoherence-free-subspace logical qubits. Together with entangled states of a different class created in Innsbruck, this work represents the current state-of-the-art for large entangled states in any qubit system.


entanglement, quantum information, Schroedinger cat state, trapped ions


Leibfried, D. , Knill, E. , Seidelin, S. , Britton, J. , Blakestad, B. , Chiaverini, J. , Hume, D. , Itano, W. , Jost, J. , Langer, C. , Ozeri, R. , Reichle, R. and Wineland, D. (2005), Creation of a six-atom Schrödinger cat state, Nature, [online], (Accessed October 17, 2021)
Created December 1, 2005, Updated January 27, 2020