Fast Dynamical Decoupling of the Mølmer-Sørensen Entangling Gate


  Amit Rotem[2]  ,  Tom Manovitz[1]  ,  Ravid Shaniv[1]  ,  Itsik Cohen[2]  ,  Yotam Shapira[1]  ,  Nitzan Akerman[1]  ,  Alex Retzker[2]  ,  Roee Ozeri[1]  
[1] Department of Physics of Complex Systems, Weizmann Institute of Science, Rehovot 76100, Israel
[2] Racah Institute of Physics, The Hebrew University of Jerusalem, Jerusalem 91904, Givat Ram, Israel

Engineering entanglement between quantum systems often involves coupling through a bosonic mediator, which should be disentangled from the systems at the operation's end.
The quality of such an operation is generally limited by environmental and control noise. One of the prime techniques for suppressing noise is by dynamical decoupling, where one actively applies pulses at a rate that is faster than the typical time scale of the noise. However, for boson-mediated gates, current dynamical decoupling schemes require executing the pulses only when the boson and the quantum systems are disentangled. This restriction implies an increase of the gate time by a factor of $\sqrt{N}$, with $N$ being the number of pulses applied .Here we propose and realize a method that enables dynamical decoupling in a boson mediated system where the pulses can be applied while spin-boson entanglement persists, resulting in an increase in time that is at most a factor of $\pi/2$, independently of the number of pulses applied. We experimentally demonstrate the robustness of our entangling gate with fast dynamical decoupling to $\sigma_z$ noise using ions in a Paul trap.