# bil 2013 quantum entanglement highlights

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2012 Quantum Entanglement Research Highlights as presented at the 2013 BIL ConferenceTRANSCRIPT

2012 Quantum Entanglement Research Highlights(or How to get some Spooky Action at a Distance) Gary V Stephenson Seculine Consulting 03 March 2013

_________________S_E_C_U_L_I_N_E_____C_O_N_S_U_L_T_I_N_G_________________

Why a Quantum Entanglement talk?

Because its a talk I wanted to hear & no one else was giving it Why is it interesting? Spooky action at a distance Why is it controversial? Non-locality still has detractors Because 2012 was a revolutionary year for quantum entanglement experiments Included in this talk are three experiments:

1) Quantum Spin Liquid (QSL) in Herbertsmithite 2) Entangled Photons in Orbital Angular Momentum (OAM) Twisted Beams 3) Canary Island Long Range Quantum State Teleportation

The focus will be on the outcomes and interpretation of each of these experiments Because it is fun and instructive to speculate on which applications are possible and which are not possible.

What is Quantum Entanglement?

1) A coupled set of quantum states Can be a large enough set of coupled states to result in a macroscopic effect 2) A source of quantum coherence Can lead to novel behavior such as super conductivity and super fluidity 3) An example of non-locality Space-time coordinates are not relevant to coupled states

A quantum state here

Both part of same qubit

Affects a quantum state here

Credit: http://www.daviddarling.info/images/quantum_entanglement.gif

Notional two state entanglement example: No decay Live cat Decay Dead cat

Credit: http://www.upscale.utoronto.ca/GeneralInterest/Harrison/SchrodCat/SchrodCat.html

Experiment #1: Quantum Spin Liquid (QSL) in Herbertsmithite

What was the experiment? Used neutron scattering to measure spin states present within the Herbertsmitite crystal What was the result? Positively confirmed coherent spin state structure within the crystal What is the significance? Measurement of macroscopic liquid quantum entanglement

Herbertsmitite, Photo Credit: Tianheng Han / MIT

Inelastic neutron scattering from the spin excitations, plotted in reciprocal space: ac, Measurements were made at T = 1.6K on a single-crystal sample of ZnCu3(OD)6Cl2. Figure 1 from Reference [1]

Experiment #2: Entangled Photons in Orbital Angular Momentum (OAM) Twisted Beams/2012/10/31/338.6107.640.DC1/Fickler.SM.pdf What was the experiment? Polarization converted to Entangled Attempt to entangle Orbital angular Polarization momentum Photon Pair Angular Momentum states of using SLM Input photon pairs (+OAM with OAM) What was the result? Successful conversion of polarization entangled photons LaguerreGaussian into OAM entangled photons to Mode OAM very high OAM numbers Entangled Photon What is the significance? Output It is now practical to couple macroscopic angular momentum (e.g. via an optical spanner) to entangled photon states False-color image of a laser beam exhibiting a superposition of Credit:http://www.sciencemag.org/content/suppl

Photo credit: Fibre-optic spanner (macro version of EO spanner), http://images.gizmag.com/hero/fib er-opticspanner.jpg

10 right-handed and 10 left-handed quanta of orbital angular momenta, making 10 + 10 = 20 bright spots on the inner ring. Photons in such modes rotate simultaneously clockwise and anticlockwise. (Courtesy: Robert Fickler, University of Vienna) [2]

Experiment #3: Canary Island Long Range Quantum State Teleportation

What was the experiment? Attempt to teleport a quantum bit (qubit) from one island to another What was the result? When the quantum state of one photon was altered, the quantum state of the second photon was altered instantaneously, faster than the speed of light, without even the smallest of delays. Proof of quantum state teleportation across distances useful in space. What is the significance? A record distance of 143 kilometers (89 miles)

Photo credit: Ref [3]

Diagram credit: X-S Ma et al. Nature 000, 1-5 (2012) doi:10.1038/nature11472

Summary & Conclusions

1) Quantum Spin Liquid (QSL) in Herbertsmithite demonstrates macroscopically entangled liquid spin states in a solid crystal 2) Entangled Photons in Orbital Angular Momentum (OAM) Twisted Beams demonstrates a light beam with a macroscopic quantity of entangled angular momentum, and a conversion mechanism from entangled polarization photons 3) Canary Island Long Range Quantum State Teleportation demonstrates a new record for the longest separation of a qubit between two entangled photons: 143 km.

Quantum Entanglement and quantum coherence may enable new applications not previously possible.

References

[1] Tian-Heng Han et al., Fractionalized excitations in the spin-liquid state of a kagome-lattice antiferromagnet, Nature, 2012, DOI: 10.1038/nature11659, at website: http://www.nature.com/nature/journal/v492/n7429/abs/nature11659.html, accessed 2/17/2013 [2] http://physicsworld.com/cws/article/news/2012/nov/01/spooky-action-withtwisted-beams, accessed 2/17/2013 [3] http://www.extremetech.com/extreme/135561-new-quantum-teleportationrecord-paves-the-way-towards-a-worldwide-quantum-network, accessed 2/17/2013 [4] QE & No-Go Theorems: http://en.wikipedia.org/wiki/Quantum_entanglement, http://en.wikipedia.org/wiki/No_communication_theorem, http://en.wikipedia.org/wiki/No-cloning_theorem, http://en.wikipedia.org/wiki/No_teleportation_theorem, all accessed 2/17/2013 [5]http://www.darpa.mil/Our_Work/MTO/Programs/Quantum_Entanglement_Scien ce_and_Technology_%28QUEST%29.aspx, accessed 2/17/2013 [6] L.-A. Wu, D. A. Lidar, and S. Schneider. Long-range entanglement generation via frequent measurements PHYSICAL REVIEW A 70, 032322 (2004)

[7] http://www.laserfocusworld.com/articles/print/volume-41/issue12/features/photonics-frontiers-entangled-photons-lsquospooky-actionrsquo-worksat-a-distance.html, accessed 2/17/2013

Backup ChartsNo Communication Theorem No Cloning Theorem No Teleportation Theorem Whats wrong with this picture? DARPAs QUEST Program

The No Communication Theorem

Description of theorem: No communication can be achieved only via a shared entangled state. Therefore shared entanglement alone can not be used to transmit any information. [4]

Quantum Channel

Photo Credit: Adapted from Quantum Entanglement in Optical Fiber, OSA, March 2008

Counter-example: Peacock and Hepburn, Begging the Signaling Question, arXiv:quant-ph/9906036v1, as referenced in [4]

The No Cloning Theorem

Description of theorem: No perfect quantum copies of arbitrary quantum states are possible. Therefore you cannot clone states. [4]

Counter-example: L.-A. Wu, D. A. Lidar, and S. Schneider, Long-range entanglement generation via frequent measurements, PHYSICAL REVIEW A 70, 032322 (2004), Ref. [6]

The No Teleportation Theorem

Description of theorem: A classical information channel can not transmit quantum information. (By transmit, we mean transmission with full fidelity.) [4]

This channel cant send qubits

but taken together these two channels can.

Counter-example: Quantum teleportation schemes may utilize both resources to achieve what is impossible for either alone, per reference [4], as demonstrated by X-S Ma et al. Nature 000, 1-5 (2012) doi:10.1038/nature11472.

Whats wrong with this picture?Find the flaw in the following thought experiment which uses the Quantum Spin Liquid (QSL) in pieces of Herbertsmithite Crystal:1) Entangle QSL in Xtal1: 3) Cleave Xtal1 and send half to Mars 5) Modulate QSL1 spin with magnetic field: 8) Readout QSL2 spin with neutron scattering

Y(t)2) Entangle QSL in Xtal2:

Y (t)4) Cleave Xtal2 and send half to Mars 6) Readout QSL1 spin with neutron scattering 7) Modulate QSL2 spin with magnetic field

Dont we now have Instantaneous, Faster Than Light (FTL), Duplex Communication between Earth and Mars?

DARPAs QUEST Program

For more info, see reference [5]: http://www.darpa.mil/Our_Work/MTO/Programs/Quantum_Entanglement_Science_and _Technology_%28QUEST%29.aspx