2012 Quantum Entanglement Research Highlights

(or How to get some Spooky Action at a Distance)

Gary V StephensonSeculine 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 it’s 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

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

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

A quantum state here

Affects a quantum state here

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

Both part of same qubit

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 liquidquantum entanglement

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

Herbertsmitite, Photo Credit: Tianheng Han / MIT

Experiment #2: Entangled Photons in Orbital Angular Momentum (OAM)

Twisted Beams What was the experiment?

Attempt to entangle Orbital Angular Momentum states of photon pairs (+OAM with –OAM)

What was the result? Successful conversion of

polarization entangled photons into OAM entangled photons to very high OAM numbers

What is the significance? It is now practical to couple

macroscopic angular momentum (e.g. via an optical spanner) to entangled photon states

Photo credit: Fibre-optic spanner (macro version of EO

spanner), http://images.gizmag.com/hero/fib

er-opticspanner.jpg

Laguerre-Gaussian

Mode OAMEntangled

PhotonOutput

False-color image of a laser beam exhibiting a superposition of 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]

Entangled Polarization Photon Pair

Input

Polarization converted to

angular momentum using SLM

Credit:http://www.sciencemag.org/content/suppl/2012/10/31/338.6107.640.DC1/

Fickler.SM.pdf

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-with-twisted-beams, accessed 2/17/2013

[3] http://www.extremetech.com/extreme/135561-new-quantum-teleportation-record-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_Science_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/issue-12/features/photonics-frontiers-entangled-photons-lsquospooky-actionrsquo-works-at-a-distance.html, accessed 2/17/2013

Backup Charts

No Communication Theorem No Cloning Theorem No Teleportation Theorem What’s wrong with this picture? DARPA’s 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]

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

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

Quantum ChannelQuantum Channel

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]

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.

This channel can’t send qubits…

…but taken together these two channels can.

What’s wrong with this picture?

Find the flaw in the following thought experiment which uses the Quantum Spin Liquid (QSL) in pieces of Herbertsmithite Crystal:

Don’t we now have Instantaneous, Faster Than Light (FTL), Duplex Communication between Earth and Mars?

(t)

’ (t)

1) Entangle QSL in Xtal1:

2) Entangle QSL in Xtal2:

3) Cleave Xtal1 and send half to Mars

4) Cleave Xtal2 and send half to Mars

5) Modulate QSL1 spin with magnetic field:

6) Readout QSL1 spin with neutron scattering 7) Modulate QSL2 spin

with magnetic field

8) Readout QSL2 spin with neutron scattering

DARPA’s QUEST Program

For more info, see reference [5]:http://www.darpa.mil/Our_Work/MTO/Programs/

Quantum_Entanglement_Science_and_Technology_%28QUEST%29.aspx