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Experimental demonstration of memory-enhanced quantum communication 期刊论文
NATURE, 2020
作者:  Quinn, Robert A.;  Melnik, Alexey, V;  Vrbanac, Alison;  Fu, Ting;  Patras, Kathryn A.;  Christy, Mitchell P.;  Bodai, Zsolt;  Belda-Ferre, Pedro;  Tripathi, Anupriya;  Chung, Lawton K.;  Downes, Michael;  Welch, Ryan D.;  Quinn, Melissa;  Humphrey, Greg;  Panitchpakdi, Morgan;  Weldon, Kelly C.;  Aksenov, Alexander;  da Silva, Ricardo;  Avila-Pacheco, Julian;  Clish, Clary;  Bae, Sena;  Mallick, Himel;  Franzosa, Eric A.;  Lloyd-Price, Jason;  Bussell, Robert;  Thron, Taren;  Nelson, Andrew T.;  Wang, Mingxun;  Leszczynski, Eric;  Vargas, Fernando;  Gauglitz, Julia M.;  Meehan, Michael J.;  Gentry, Emily;  Arthur, Timothy D.;  Komor, Alexis C.;  Poulsen, Orit;  Boland, Brigid S.;  Chang, John T.;  Sandborn, William J.;  Lim, Meerana;  Garg, Neha;  Lumeng, Julie C.;  Xavier, Ramnik J.;  Kazmierczak, Barbara, I;  Jain, Ruchi;  Egan, Marie;  Rhee, Kyung E.;  Ferguson, David;  Raffatellu, Manuela;  Vlamakis, Hera;  Haddad, Gabriel G.;  Siegel, Dionicio;  Huttenhower, Curtis;  Mazmanian, Sarkis K.;  Evans, Ronald M.;  Nizet, Victor;  Knight, Rob;  Dorrestein, Pieter C.
收藏  |  浏览/下载:36/0  |  提交时间:2020/07/03

The ability to communicate quantum information over long distances is of central importance in quantum science and engineering(1). Although some applications of quantum communication such as secure quantum key distribution(2,3) are already being successfully deployed(4-7), their range is currently limited by photon losses and cannot be extended using straightforward measure-and-repeat strategies without compromising unconditional security(8). Alternatively, quantum repeaters(9), which utilize intermediate quantum memory nodes and error correction techniques, can extend the range of quantum channels. However, their implementation remains an outstanding challenge(10-16), requiring a combination of efficient and high-fidelity quantum memories, gate operations, and measurements. Here we use a single solid-state spin memory integrated in a nanophotonic diamond resonator(17-19) to implement asynchronous photonic Bell-state measurements, which are a key component of quantum repeaters. In a proof-of-principle experiment, we demonstrate high-fidelity operation that effectively enables quantum communication at a rate that surpasses the ideal loss-equivalent direct-transmission method while operating at megahertz clock speeds. These results represent a crucial step towards practical quantum repeaters and large-scale quantum networks(20,21).


A solid-state spin memory is used to demonstrate quantum repeater functionality, which has the potential to overcome photon losses involved in long-distance transmission of quantum information.


  
Current-driven magnetic domain-wall logic 期刊论文
NATURE, 2020, 579 (7798) : 214-+
作者:  Culp, Elizabeth J.;  Waglechner, Nicholas;  Wang, Wenliang;  Fiebig-Comyn, Aline A.;  Hsu, Yen-Pang;  Koteva, Kalinka;  Sychantha, David;  Coombes, Brian K.;  Van Nieuwenhze, Michael S.;  Brun, Yves, V;  Wright, Gerard D.
收藏  |  浏览/下载:31/0  |  提交时间:2020/07/03

Spin-based logic architectures provide nonvolatile data retention, near-zero leakage, and scalability, extending the technology roadmap beyond complementary metal-oxide-semiconductor logic(1-13). Architectures based on magnetic domain walls take advantage of the fast motion, high density, non-volatility and flexible design of domain walls to process and store information(1,3,14-16). Such schemes, however, rely on domain-wall manipulation and clocking using an external magnetic field, which limits their implementation in dense, large-scale chips. Here we demonstrate a method for performing all-electric logic operations and cascading using domain-wall racetracks. We exploit the chiral coupling between neighbouring magnetic domains induced by the interfacial Dzyaloshinskii-Moriya interaction(17-20), which promotes non-collinear spin alignment, to realize a domain-wall inverter, the essential basic building block in all implementations of Boolean logic. We then fabricate reconfigurable NAND and NOR logic gates, and perform operations with current-induced domain-wall motion. Finally, we cascade several NAND gates to build XOR and full adder gates, demonstrating electrical control of magnetic data and device interconnection in logic circuits. Our work provides a viable platform for scalable all-electric magnetic logic, paving the way for memory-in-logic applications.


  
Fast two-qubit logic with holes in germanium 期刊论文
NATURE, 2020, 577 (7791) : 487-+
作者:  Halpin-Healy, Tyler S.;  Klompe, Sanne E.;  Sternberg, Samuel H.;  Fernandez, Israel S.
收藏  |  浏览/下载:28/0  |  提交时间:2020/07/03

Universal quantum information processing requires the execution of single-qubit and two-qubit logic. Across all qubit realizations(1), spin qubits in quantum dots have great promise to become the central building block for quantum computation(2). Excellent quantum dot control can be achieved in gallium arsenide(3-5), and high-fidelity qubit rotations and two-qubit logic have been demonstrated in silicon(6-9), but universal quantum logic implemented with local control has yet to be demonstrated. Here we make this step by combining all of these desirable aspects using hole quantum dots in germanium. Good control over tunnel coupling and detuning is obtained by exploiting quantum wells with very low disorder, enabling operation at the charge symmetry point for increased qubit performance. Spin-orbit coupling obviates the need for microscopic elements close to each qubit and enables rapid qubit control with driving frequencies exceeding 100 MHz. We demonstrate a fast universal quantum gate set composed of single-qubit gates with a fidelity of 99.3 per cent and a gate time of 20 nanoseconds, and two-qubit logic operations executed within 75 nanoseconds. Planar germanium has thus matured within a year from a material that can host quantum dots to a platform enabling two-qubit logic, positioning itself as an excellent material for use in quantum information applications.


Spin qubits based on hole states in strained germanium could offer the most scalable platform for quantum computation.