Decoherence-protected memory for a single-photon qubit

Distributed quantum computation in a quantum network1–3 is based on the idea that qubits can be preserved and efficiently exchanged between long-lived, stationary network nodes via photonic links4. Although long qubit lifetimes have been observed5–10, and non-qubit excitations have been memorized11–14, the long-lived storage and efficient retrieval of a photonic qubit by means of a light–matter interface15–20 remains an outstanding challenge. Here, we report on a qubit memory based on a single atom coupled to a high-finesse optical resonator. By mapping the qubit between an interface basis with strong light–matter coupling and a memory basis with low decoherence, we achieve a coherence time exceeding 100 ms with a time-independent storage-and-retrieval efficiency of 22%. The former constitutes an improvement by two orders of magnitude21,22 and thus implements an efficient photonic qubit memory with a coherence time that exceeds the lower bound needed for direct qubit teleportation in a global quantum internet.A quantum memory based on a rubidium atom shows a record-long storage time of 100 ms with a readout efficiency of 22%. The photonic qubit is transferred between a basis with strong light–matter coupling and a basis with low decoherence.

[1]  Y. O. Dudin,et al.  A quantum memory with telecom-wavelength conversion , 2010 .

[2]  Christian Nölleke,et al.  Ground-state cooling of a single atom at the center of an optical cavity. , 2012, Physical review letters.

[3]  Stephan Ritter,et al.  An integrated quantum repeater at telecom wavelength with single atoms in optical fiber cavities , 2015, 1507.07849.

[4]  J. Cirac,et al.  Experimental demonstration of quantum memory for light , 2004, Nature.

[5]  H. J. Kimble,et al.  The quantum internet , 2008, Nature.

[6]  Kae Nemoto,et al.  Quantum communication without the necessity of quantum memories , 2012, Nature Photonics.

[7]  Manjin Zhong,et al.  Optically addressable nuclear spins in a solid with a six-hour coherence time , 2015, Nature.

[8]  M. L. W. Thewalt,et al.  Quantum Information Storage for over 180 s Using Donor Spins in a 28Si “Semiconductor Vacuum” , 2012, Science.

[9]  J. Cirac,et al.  Room-Temperature Quantum Bit Memory Exceeding One Second , 2012, Science.

[10]  Stephan Ritter,et al.  Interference and dynamics of light from a distance-controlled atom pair in an optical cavity , 2016, Nature Photonics.

[11]  N. Lutkenhaus,et al.  Quantum repeaters with imperfect memories: Cost and scalability , 2008, 0810.5334.

[12]  Kunpeng Wang,et al.  Coherence Preservation of a Single Neutral Atom Qubit Transferred between Magic-Intensity Optical Traps. , 2016, Physical review letters.

[13]  Jian-Wei Pan,et al.  A millisecond quantum memory for scalable quantum networks , 2008, 0807.5064.

[14]  Charles H. Bennett,et al.  Teleporting an unknown quantum state via dual classical and Einstein-Podolsky-Rosen channels. , 1993, Physical review letters.

[15]  Christian Nölleke,et al.  A single-atom quantum memory , 2011, Nature.

[16]  Simon Baur,et al.  Bose-Einstein condensate as a quantum memory for a photonic polarization qubit , 2011, 1112.4733.

[17]  A. Rauschenbeutel,et al.  Storage of fiber-guided light in a nanofiber-trapped ensemble of cold atoms , 2015, 1502.01151.

[18]  Wolfgang Dür,et al.  Quantum Repeaters: The Role of Imperfect Local Operations in Quantum Communication , 1998 .

[19]  D Budker,et al.  Solid-state electronic spin coherence time approaching one second , 2012, Nature Communications.

[20]  D. DiVincenzo,et al.  The Physical Implementation of Quantum Computation , 2000, quant-ph/0002077.

[21]  Axel Kuhn,et al.  Single-photon absorption in coupled atom-cavity systems , 2011, 1105.1699.

[22]  Bo Zhao,et al.  Efficient and long-lived quantum memory with cold atoms inside a ring cavity , 2012, Nature Physics.

[23]  C Langer,et al.  Long-lived qubit memory using atomic ions. , 2005, Physical review letters.

[24]  J Laurat,et al.  Demonstration of a memory for tightly guided light in an optical nanofiber. , 2015, Physical review letters.

[25]  A. D. Boozer,et al.  Cooling to the ground state of axial motion for one atom strongly coupled to an optical cavity. , 2006, Physical review letters.

[26]  Jian-Wei Pan,et al.  An efficient quantum light–matter interface with sub-second lifetime , 2015, Nature Photonics.

[27]  F. Schmidt-Kaler,et al.  A long-lived Zeeman trapped-ion qubit , 2016, 1606.07220.

[28]  C. Xie,et al.  Long lifetime and high-fidelity quantum memory of photonic polarization qubit by lifting zeeman degeneracy. , 2013, Physical review letters.

[29]  J. Laurat,et al.  Mapping photonic entanglement into and out of a quantum memory , 2007, Nature.

[30]  Tilo Steinmetz,et al.  Coherence in microchip traps. , 2004, Physical review letters.

[31]  N. Gisin,et al.  Quantum storage of heralded polarization qubits in birefringent and anisotropically absorbing materials. , 2012, Physical review letters.

[32]  W. S. Kolthammer,et al.  Broadband single-photon-level memory in a hollow-core photonic crystal fibre , 2014, Nature Photonics.