Mr.Jack Zhang(Ph.D.) has been focusing on the quantum computing and quantum network by the system of trapped ion and related quantum photonics technology, to achieve the goal of establishing the distributed quantum computer on a long term scale.
The Trapped Ion Quantum Network Research and Achievements
The ion trap system is a combination of electric or magnetic fields used to capture charged particles. We have successfully developed two trapped Yb+ ion systems(Needle trap and the Paul trap) for single and multi-ions research respectively. The system is including an Ultra High Vacuum Environment (below 1e-12torr) to isolate the single charged atom ion from the external environment. By four different wavelengths lasers along with the optical systems, the quantum information can be stored and computed on with the atom ion. The microscopic objective lens with NA~0.4 is designed to collect and determine the quantum state with the total efficiency of 1.1% (take into account that probing detector 30% efficiency and the transmission effectiveness at 90%). Alternatively, with a higher Numerical Aperture objective lens, resulting in a deterministic better collective efficiency further greater readout fidelity of the quantum information. The ion coherence time of T1 tested is 77ms, having the system upgraded, Jack and Hyperion Optics together developed an NA0.7 micro-objective lens. It is not only to increase the photon collective efficiency but also to implement the single ion addressing in the multi-ion chain.
Ion-ion ought to be entangled to achieve a deterministic quantum network. Mr.Jack Zhang developed a revolutionary fiber-based FP cavity technology which is aiming at remarkably increasing the photon collecting efficiency (collected into the fiber) up to 60% @369nm wavelength( Submitted to Applied Physics Letter).Aided by self-developed technology, the extraordinary collecting efficiency secures a significant rate of ions entangling.( The Chris Monroe group is achieve only 10% lens collection efficiency and the fiber coupling effiency is only 0.14, Nat. Phys. 11, 37 (2015) ) Further, If a strong coupling between cavity and ion can be accomplished, it will form a significative foundation to serve the purpose of creating valuable access for a wide range of physics research.
Mr.Jack Zhang successfully developed a reliable needle electrodes fabrication method to study the relationship between surface roughness and the ion heating rate. This method can easily fabricate the needle electrodes with a desiring surface roughness, and it grants an issued patent #ZL201410379919.6
For the physics research, a quantum simulation is performed using the ion trap(arXiv 1505.05734) which applies the Kibble-Zurek mechanism to quantum Ising model.
Quantum Photonics Achievements
To approach a large scaled quantum computer, We require entangling a vast number of qubits. The photon is an ideal information carrier to entangle the remote qubits, e.g. quantum dots NV center or ions and photon etc. Mr.Jack Zhang’s group developed the photon system, and his team is the very first group which generating eight photons entangled GHZ state in the world (Nat. Comm. 2, 546 (2011)). This photon entangled source is critically bright (OL 33(9) 968 (2008), PRL 115, 260402 (2015)).
Adopting the technology of entangled photons, and regarding photon as an entanglement carrier, Mr.Jack Zhang would expect the ion can be entangled in the same way as photos shortly.