# QUSCOPE seminar - Itsik Cohen: Refocusing schemes of two qubit gates for trapped ions

## Info about event

### Time

**Abstract: **Entanglement between two trapped ions is carried via a vibrational phonon mediator. This relatively slow, second order interaction is usually most fragile to noise effects, e.g., single body noise terms and two body noise terms. To compensate for single body noise effects during the two-qubit interaction, dynamical decoupling pulses are often applied at times when the qubits are disentangled from the phonon bus. Therefore, applying dynamical decoupling pulses with Ω_{r} repetition rate, to refocus a lower frequency noise, would prolong the gate duration linearly with Ω_{r}. In the first part of my talk I will show how to utilize dynamical decoupling pulses, such that the phonon-mediated entangling gate is performed in the strong coupling regime; namely, the gate duration is increased by a reduced factor of less than π/2.

On the other hand, compensating for the amplitude noise, which inflicts a random two qubit term, has proven more challenging. The main obstacle is that the two body noise time scale is shorter than the two qubit gate itself which prevents the use of standard refocusing methods. In the second part of my talk I will present two approaches to tackle this problem. The first one makes the use of composite pulses, applied as dynamical decoupling on the building blocks of ultrafast entangling gates; whereas the second approach uses a measurement and feedback based method to refocus two qubit gates.

There is coffee/tea and bread rolls from 10:00 .