Quantum gate teleportation between separated zones of a trapped-ion processor

主讲人 (Speaker): 

万雍

主讲人单位 (Speaker's Institute): 

National Institute of Standards and Technology

邀请人 (Invited by): 

罗乐

时间 (Time): 

星期五, 2019/03/08 - 10:00 to 12:00

地点 (Location): 

珠海校区海滨红楼17栋107 (Rm 107, Red House 17)

摘要 (Abstract): 

        Scaling up trapped-ion quantum information processors implies that above some size, qubits will likely need to be distributed across multiple processing zones. Harnessing the full power of such an architecture for quantum information processing requires a method to connect qubits in separate locations. The “quantum charge-coupled device” architecture [1,2] allows to couple distant qubits by first physically moving them together, but at the same time imposes overhead from time spent on shuttling ions. An alternative solution is to employ a teleported two-qubit entangling gate [3,4] that uses only local operations in two separate locations, classical communication between these locations, and a shared entangled qubit pair as a resource. This approach has been demonstrated probabilistically in photonic systems with post-selection and only recently performed deterministically between two superconducting cavity qubits by means of an entangled pair of transmons [5]. Here we demonstrate a deterministic teleported CNOT gate between two beryllium ion qubits in spatially separated zones of a segmented Paul trap, using an entangled pair of magnesium ion qubits as the resource. We perform full process tomography on the two beryllium ions, and infer a 95% confidence interval [0.845, 0.872] for the CNOT entanglement fidelity using maximum likelihood (ML) estimation. To characterize consistency with a single quantum process and to discover unchecked fluctuations, we apply a likelihood-ratio test to the tomography data [6, 7], which indicates an unexpected level of inconsistency. We verify through numerical simulation and independent measurements on the experimental setup that slow drifts in some laser beamlines was likely the cause of this inconsistency, suggesting the importance of such consistency checks in addition to other benchmarking techniques.

        Our experiments combine ion shuttling [8] with individually-addressed single qubit rotations and detection, high fidelity same- and mixed-species two qubit gates [9,10], and real-time conditional operations, thereby demonstrating a substantial fraction of the building blocks necessary for scaling trapped-ion quantum information processors.

主讲人简介 (Speaker's CV): 

Yong Wan My research interest lies in quantum information processing using trapped atomic ions. Using multiple atomic species as computation and ancilla ions, scalable architecture such as quantum charge-coupled device (QCCD) can be implemented using segmented ion traps. This approach allows to solve problems intractable on classical computer. Education 07/2014 Doctor of Natural Sciences, University of Hannover, Hannover, Germany. 03/2010 Diploma in Physics, University of Stuttgart, Stuttgart, Germany. 06/2007 Bachelor of Science, Wuhan University, Wuhan, China. 08/2014–Now Research Associate, National Institute of Standards and Technology, Boulder,Colorado, USA. Affiliated with From 08/2014–05/2016 Research Laboratory of Electronics, Massachusetts Institute of Technology, Cambridge, Massachusetts, USA. From 06/2016–Now Department of Physics, University of Colorado, Boulder, CO,USA. Research topic: Quantum information processing using trapped ions in segmented Paul trap Supervisors: Prof. Dave J. Wineland Achievements:Implementation of complete set of transport primitives for scalable quantum information processing.- Implemented basic ion transport primitives of 9Be+ ions in a segmented ion trap including shuttling through a X-junction and separation of two 9Be+ ions.- Re-ordering of a two-ion crystal of 9Be+ ions using the transport primitives and the X-junction, which could be generalized to a long ion chain, allowing quantum operations on arbitrarily ordered and divided sub-sets of ions. Demonstrate high fidelity two-qubit gates between two 9Be+ ions. Utilizing a high-power Raman laser system and a low-noise ion trap, the major errors of the laser-based entangling gates in the ion trap (from spontaneous emission and anomalous heating) are reduced and an infidelity down to 1 × 10−3 is demonstrated.