Experimental quantum teleportation Dirk Bouwmeester, Jian‐Wei Pan, Klaus Mattle, Manfred Eibl, Harald Weinfurter & Anton Zeilinger NATURE | VOL 390 | 11 DECEMBER 1997 Overview • Motivation • General theory behind teleportation • Experimental setup • Applications of teleportation • New research from this study Relaying quantum information is difficult Sending directly can take a lot of time Coherence can be lost in the transfer We can’t just measure a particle’s state and then reconstruct, because‐‐ Each state is a superposition of many states. Once we measure the particle, it will collapse into only one state, and all the other information is lost For example, a photon can be polarized or in a superposition of polarized states. Beam Splitter: horizontally polarized photons are reflected, vertically polarized photons are transmitted The measurement projects the photon onto one polarization or the other, and we lose information about the original state So, if we want to replicate the state, we can’t just measure and reconstruct… But we can use entanglement to replicate the state by quantum teleportation. We have Alice, with a particle in state <ψ1|. She wants to transfer it to Bob. Bob and Alice also have particles 2 and 3, which are entangled. …if Alice can entangle particle 1 and particle 2, …then particle 3 should be in the same state as the original particle 1. But how can we do this experimentally? Experimental verification of teleportation theory ‐1993: Bennett et al. suggest it is possible to transfer the state of one particle to another using entanglement Meanwhile: Quantum computing and cryptography develop ‐1995: Kwiat et al. build a bright entanglement source ‐1997: Bouwmeester et al. demonstrate experimental Spontaneous parametric downconversion teleportation provides a bright source of entangled photons Source: Wikimedia Commons Teleportation has been achieved, but • Initial state is destroyed on Alice’s side during teleportation (don’t try this on yourself!) • Bell‐state measurement has four outcomes, including the desired antisymmetric state – Teleportation occurs just 25% of the time, 100% with extra classical information (slower) Desired state after measurement Other possible outcomes But this kind of teleportation is good enough • Complete basis of states can be teleported, allowing teleportation of general states • Applications in quantum information: – Quantum memory – Data transfer through poor connections without losses – Needs work, though: improved data rate? • New science: – Bell test on particles with no Common past Citation Analysis Since its publication in 1997, it have been sited for 1991 times. Citation 1200 1088 180 1000 160 140 800 120 100 600 470 80 400 60 Citation 40 137 115 200 77 70 20 34 0 0 ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ ‐ Ci 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011.10.9 Citation by Year Citation By Journal Recent Progress in Quantum Teleportation Experiments After the first Innsbruck experiment • 2003‐Experimental realization of freely propagating teleported qubits Jian‐Wei Pan et al., Nature 421 (2003) 721‐725 • 2004‐Experimental demonstration of five‐photon entanglement and open‐destination teleportation Zhi Zhao, et al. Nature 430, 54‐58 (1 July 2004) • 2006‐Experimental entanglement of six photons in graph states Chao‐Yang Lu, et al. Nature Physics 3, 91 ‐ 95 (2007) Recent Progress in Quantum Teleportation Experiments (Continued) • 2008‐Memory‐built‐in quantum teleportation with photonic and atomic qubits Yu‐Ao Chen, et al, Nature Physics 4, 103 ‐ 107 (2008) Experimental set‐up for teleportation between photonic and atomic qubits. Recent Progress in Quantum Teleportation Experiments (continued) • 2010‐Quantum teleportation achieved over 16 km University of Science and Technology of China, Tsinghua University (PhysOrg.com) ‐‐ Scientists in China have succeeded in teleporting information between photons further than ever before. They transported quantum information over a free space distance of 16 km (10 miles), much further than the few hundred meters previously achieved, which brings us closer to transmitting information over long distances without the need for a traditional signal. Summary • Observed teleportation of photon polarization states • Teleportation can be used to realize a quantum computer • Fueled new research involving more photons and information transfer between different particles.