arXiv subjects

You-Jin Deng

Publications and source records attributed to You-Jin Deng.

4 recordsLinked to original sources

arXiv2020

Cooling and entangling ultracold atoms in optical lattices

Scalable, coherent many-body systems can enable the realization of previously unexplored quantum phases and have the potential to exponentially speed up information processing. Thermal fluctuations are negligible and quantum effects govern the behavior of such systems with extremely low temperature. We report the cooling of a quantum simulator with 10,000 atoms and mass production of high-fidelity entangled pairs. In a two-dimensional plane, we cool Mott insulator samples by immersing them into removable superfluid reservoirs, achieving an entropy per particle of $1.9^{+1.7}_{-0.4} \times 10^{-3} k_{\text{B}}$. The atoms are then rearranged into a two-dimensional lattice free of defects. We further demonstrate a two-qubit gate with a fidelity of 0.993 $\pm$ 0.001 for entangling 1250 atom pairs. Our results offer a setting for exploring low-energy many-body phases and may enable the creation of large-scale entanglement

cond-mat.quant-gas↗

arXiv2014

Experimental Determination of the Finite-Temperature Phase Diagram of a Spin-Orbit Coupled Bose Gas

Spin-orbit (SO) coupling has led to numerously exciting phenomena in electron systems, for instance, the recently discovered topological insulator. The synthesized SO coupling with ultracold neutral atoms opens a new avenue of quantum simulation, and gives us an opportunity to study SO coupling in bosonic systems. Indeed, SO coupling leads to many new phenomena of boson superfluidity and various condensate phases that spontaneously break different symmetries. A richer structure of symmetry breaking always results in a nontrivial finite-temperature phase diagram. While the thermodynamics of the SO coupled Bose gas at finite temperature is still unknown either in theory or experiment. In this work, we experimentally generate the SO coupling in ultracold Rb-87 gas to explore in a large temperature range and get most key features. We discover a novel phase transition between the stripe ordered phase and the magnetized phase, which is reminiscent of temperature-driven transition from the B phase to the A phase in super- fluid Helium-3 and from spin-density-wave to spin nematic transition in iron pnictide. We also observe that the magnetic phase transition and the Bose condensate transition occur simultaneously as temperature decreases. Our work determines the entire finite-temperature phase diagram of SO coupled Bose gas and further demonstrate the power of quantum simulation.

cond-mat.quant-gas↗

arXiv2012

Holographic Storage of Biphoton Entanglement

Coherent and reversible storage of multi-photon entanglement with a multimode quantum memory is essential for scalable all-optical quantum information processing. Although single photon has been successfully stored in different quantum systems, storage of multi-photon entanglement remains challenging because of the critical requirement for coherent control of photonic entanglement source, multimode quantum memory, and quantum interface between them. Here we demonstrate a coherent and reversible storage of biphoton Bell-type entanglement with a holographic multimode atomic-ensemble-based quantum memory. The retrieved biphoton entanglement violates Bell's inequality for 1 microsecond storage time and a memory-process fidelity of 98% is demonstrated by quantum state tomography.

quant-ph↗

arXiv2012

Experimental demonstration of topological error correction

Scalable quantum computing can only be achieved if qubits are manipulated fault-tolerantly. Topological error correction - a novel method which combines topological quantum computing and quantum error correction - possesses the highest known tolerable error rate for a local architecture. This scheme makes use of cluster states with topological properties and requires only nearest-neighbour interactions. Here we report the first experimental demonstration of topological error correction with an eight-photon cluster state. It is shown that a correlation can be protected against a single error on any qubit, and when all qubits are simultaneously subjected to errors with equal probability, the effective error rate can be significantly reduced. This demonstrates the viability of topological error correction. Our work represents the first experimental effort to achieve fault-tolerant quantum information processing by exploring the topological properties of quantum states.

quant-ph↗