Quantum teleportation and entanglement distribution over 100-kilometre free-space channels

Abstract

Transferring an unknown quantum state over arbitrary distances is essential for large-scale quantum communication and distributed quantum networks. It can be achieved with the help of long-distance quantum teleportation and entanglement distribution. The latter is also important for fundamental tests of the laws of quantum mechanics. Although quantum teleportation and entanglement distribution over moderate distances have been realized using optical fibre links, the huge photon loss and decoherence in fibres necessitate the use of quantum repeaters for larger distances. However, the practical realization of quantum repeaters remains experimentally challenging. Free-space channels, first used for quantum key distribution, offer a more promising approach because photon loss and decoherence are almost negligible in the atmosphere. Furthermore, by using satellites, ultra-long-distance quantum communication and tests of quantum foundations could be achieved on a global scale. Previous experiments have achieved free-space distribution of entangled photon pairs over distances of 600 metres (ref. 14) and 13 kilometres (ref. 15), and transfer of triggered single photons over a 144-kilometre one-link free-space channel. Most recently, following a modified scheme, free-space quantum teleportation over 16 kilometres was demonstrated with a single pair of entangled photons. Here we report quantum teleportation of independent qubits over a 97-kilometre one-link free-space channel with multi-photon entanglement. An average fidelity of 80.4 ± 0.9 per cent is achieved for six distinct states. Furthermore, we demonstrate entanglement distribution over a two-link channel, in which the entangled photons are separated by 101.8 kilometres. Violation of the Clauser-Horne-Shimony-Holt inequality is observed without the locality loophole. Besides being of fundamental interest, our results represent an important step towards a global quantum network. Moreover, the high-frequency and high-accuracy acquiring, pointing and tracking technique developed in our experiment can be directly used for future satellite-based quantum communication and large-scale tests of quantum foundations.

Efficient Teleportation Between Remote Single-Atom Quantum Memories

“…Therefore, quantum repeater schemes have been proposed to establish long-distance entanglement using photons and memories [3,4]. This entanglement can then be used as a resource for the transfer of quantum information via teleportation [5].The underlying principle of teleportation was first realized with photonic qubits [6][7][8] and since then has been exploited in many experiments [9,10]. Teleportation between matter qubits was first achieved with trapped ions [11,12], albeit over a distance limited to a few micrometers owing to the short-range Coulomb interaction.…”

“…The underlying principle of teleportation was first realized with photonic qubits [6][7][8] and since then has been exploited in many experiments [9,10]. Teleportation between matter qubits was first achieved with trapped ions [11,12], albeit over a distance limited to a few micrometers owing to the short-range Coulomb interaction.…”

Device-independent certification of the teleportation of a qubit

“…Popescu proved that, if Alice and Bob share no entanglement, the average fidelity for the teleportation of unknown qubit states is bounded byF = 2 3 [2]. This bound has been widely used as a benchmark for experiments [3,4], including the most recent ones [5,6]. The bound at 2 3 holds if one trusts that the quantum systems under study are qubits.…”

“…∀ a x , ∃ a B x s.t. R c0c1 V c0c1 ( a x ) = a B x ; along with Eqn (5). To construct such a protocol, we recall that the CHSH function we derived earlier (in particular, the specific coarse graining to determine α) picks out a particular component of each of the teleported a B…”

Narrowband Biphotons: Generation, Manipulation, and Applications

“…Entangled photon pairs, termed biphotons, have been benchmark tools in the field of quantum optics for testing fundamental quantum mechanics as well as for developing applications in quantum information technology, including realization of the Einstein-Podolsky-Rosen paradox [1,2], test of violation of Bell's inequality [3,4,5], quantum cryptography and key distribution [6], quantum teleportation [7,8], quantum computation [9], etc. Traditional methods of producing biphotons include spontaneous parametric down conversion (SPDC) [10,11,12] and spontaneous four-wave mixing (SFWM) [13,14,15] in nonlinear solid-state materials.…”