Speaker
Description
Quantized motional states of trapped ions are a quantum degree of freedom that is emerging as a platform for applications such as quantum computing and quantum simulation that involve bosonic degrees of freedom. One important tool, useful for example in quantum error correction, is parity measurement. Non-destructive measurements of the parity of a motional state enable mid-circuit projections into eigenstates of parity and can be used for example in bosonic stabilizer error correction schemes. However, ion internal state measurements typically rely on conditional fluorescence of an ion, “bright” or “dark”. The state of a motional mode will generally not be preserved after “bright” detection due to motional heating when the ion experiences thousands of photon recoils.
To preserve motional information upon measurement, we engineer the motional modes of a multi-species ion chain and entangle the internal state of an ion with a motional state of a mode in which this ion does not participate. This enables protection of the motional state from decoherence due to photon recoils when the ion fluoresces. We aim to demonstrate non-destructive parity measurements and apply them to create and characterize motional “Schrödinger’s cat” states in a mixed-species ion crystal of 9Be+-25Mg+-9Be+. We entangle motional states with two internal states of the Mg+ ion using a parity operation. This parity operation is implemented with a simple ion trapping tool, a Raman carrier pulse, making use of its motional dependence due to a finite Lamb-Dicke parameter. The motional states are then swapped from the motional mode on which the entanglement was performed to a “protected” motional mode, in which the Mg+ ion does not participate, by applying oscillating fields to the trap electrodes that coherently couple the two modes. Fluorescence detection on the Mg+ ion projects it to a particular internal and motional state and avoids the effects of photon recoil on the protected mode. A coherent state of motion whose parity is measured in this way will be projected into either an even or odd motional cat state, with the cat-state parity heralded non-destructively by the measurement. The parity can subsequently be verified by a second, destructive or non-destructive, measurement.
I will show results of critical steps needed to realize this protocol, including the entanglement of states on a single ion and on a multi-ion chain, Wigner function tomography of non-classical motional states on a single ion, and protection of the motional parity from detection by using motional mode-mode coupling on a multi-ion chain.
| Academic level | PhD student |
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