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Q: Fachverband Quantenoptik und Photonik
Q 33: Quantum Effects: Entanglement and Decoherence I
Q 33.7: Talk
Wednesday, March 2, 2016, 12:30–12:45, f442
Multi-qubit Zeno subspaces through repetitive projections — •Norbert Kalb1, Julia Cramer1, Daniel Twitchen2, Matthew Markham2, Ronald Hanson1, and Tim Taminiau1 — 1QuTech and Kavli Institute of Nanoscience, Delft, The Netherlands — 2Element Six Innovation, Oxford, United Kingdom
Quantum superposition states are susceptible to decoherence due to interactions with the environment. Generally, these interactions are uncontrolled and undesired: they cause a rapid loss of the phase of the quantum state and the associated information. Here we experimentally demonstrate that adding a strong channel of decoherence in the form of repeated projections of multi-qubit operators can actually protect complex quantum states from environmental decoherence.
We create quantum states of up to three 13C nuclear spins in diamond [1] using a nitrogen vacancy center and repetitively project a joint observable of the nuclear spins. This projection freezes the unwanted evolution due to the environment through the Quantum Zeno effect, while leaving the remaining degrees of freedom available to encode multiple protected logical quantum bits, including entangled states. We quantify the suppression of dephasing through the derivation and experimental verification of a number-independent scaling law. This result enables the exploration of quantum computations with multiple logical quantum bits and studying complex spin dynamics under engineered decoherence.
[1] T.H. Taminiau et al., Nature Nanotech. 9, 171, 2014