Quantum quest: The rise of quantum information Quantum quest: The rise of quantum information Prof. Andrew White University of Queensland Brisbane, Australia quantum.info Prof. Howard Burton Perimeter Institute Waterloo, Canada Prof. Gerard Milburn University of Queensland, Brisbane, Australia Prof. Raymond Laflamme University of Waterloo, Waterloo, Canada IQCIQC 5th World Conference of Science Journalists, Melbourne 2007

quantum.info Foot Head Fun bit in the middle Melbourne Cairns Brisbane

quantum.info The Quantum Revolution Two weird things Wave-particle duality Entanglement “…a phenomena which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.” Richard Feynman “I would not call that one, but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.” Erwin Schrödinger Nobel Prize 1965 Nobel Prize 1933

quantum.info The Quantum Revolution Two weird things Wave-particle duality Entanglement “…a phenomena which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.” Richard Feynman “I would not call that one, but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.” Erwin Schrödinger Nobel Prize 1965 Nobel Prize 1933

quantum.info Things, stuff … atoms, planets, frogs… know where things are Waves Particles know where things go calm choppy Discrete – can count them waves interfere

quantum.info 1670 Light travels in straight lines What is light? Newton 1800 Light has interference fringes. Particle Wave Young

quantum.info What is light?

quantum.info 1670 Light travels in straight lines What is light? Newton 1800 Light has interference fringes Light is alternating electric and magnetic fields. Particle Wave Young Maxwell 1905 Many effects have 1 explanation Einstein Black-body radiation (Planck, 1900) Photoluminescence Photoelectric effect Ionisation of gases by UV light Black-body radiation (Planck, 1900) Photoluminescence Photoelectric effect Ionisation of gases by UV light

quantum.info Who is correct?

quantum.info Who is correct? “a candle burning at a distance slightly exceeding a mile” 1909 Even feeble light sources cause interference fringes G I Taylor

quantum.info “click” What is light? half-silvered mirror 50% light acts like it is a particle

quantum.info What is light? half-silvered mirror 25% full-silvered mirror half-silvered mirror 50% block light acts like it is a particle

quantum.info What is light? half-silvered mirror 100% 0% full-silvered mirror full-silvered mirror half-silvered mirror How can a particle do this? Particles can’t … waves can

quantum.info What is light? 100% 0% + half-silvered mirror full-silvered mirror full-silvered mirror

quantum.info 100% What is light? 0% Maybe we can trick the photon? light acts like it is a wave half-silvered mirror full-silvered mirror full-silvered mirror

quantum.info What is light? half-silvered mirror full-silvered mirror full-silvered mirror half-silvered mirror

quantum.info What is light? 25% block half-silvered mirror full-silvered mirror full-silvered mirror half-silvered mirror

quantum.info Wave/particle duality half-silvered mirror 100% 0% full-silvered mirror full-silvered mirror half-silvered mirror light can act as a particle or a wave …it depends on the experiment everything neutrons electrons atoms molecules, Na 2 bucky ball molecules, C 60, C 70 viruses… block

quantum.info weird? useful… Quantum technologies use the wave/particle duality

quantum.info The Quantum Revolution Two weird things Wave-particle duality Entanglement “…a phenomena which is impossible, absolutely impossible, to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery.” Richard Feynman “I would not call that one, but rather the characteristic trait of quantum mechanics, the one that enforces its entire departure from classical lines of thought.” Erwin Schrödinger Nobel Prize 1965 Nobel Prize 1933

quantum.info Entanglement Term coined by Schrödinger in 1935 (better in German: Entwinement) Correlations between things that defy common sense Weird … needs an analogy …

quantum.info Schrödinger’s Catfish Schrödinger’s Cat

quantum.info Entanglement Entanglement suggested to Einstein that Quantum Mechanics is incomplete “Hidden variable” theory 15 May 1935 Quantum mechanics is flawed EPR Paper While we have shown [it] does not provide a complete description of the physical reality, we left open the question of whether or not such a description exists. We believe however, that such a theory is possible.

quantum.info Entanglement I felt that Einstein's intellectual superiority over Bohr, in this instance, was enormous; a vast gulf between the man who saw clearly what was needed, and the obscurantist. John Bell 15 May 1964 If there are hidden variables, then something is happening faster than light Bell’s inequalities

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy measures Left conveyor Ricky measures Right conveyor Kwiat and Hardy, American Journal of Physics 68, 33, (2000)

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy measures Left conveyor Ricky measures Right conveyor For each cake-pair they each randomly choose to measure EITHER at half-way, the state of the cakeRisen / Flat

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy measures Left conveyor Ricky measures Right conveyor For each cake-pair they each randomly choose to measure EITHER at half-way, the state of the cakeRisen / Flat at end, the taste of the cakeGood / Bad So they measure:state / state (25%)state / taste (25%) taste / state (25%)taste / taste (25%)

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy and Ricky find that 10% of the time both cakes are Risen (RR)

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy and Ricky find that 10% of the time both cakes are Risen (RR) Whenever Lucy’s cake is Risen, Ricky’s cake tastes Good (RG)

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy and Ricky find that 10% of the time both cakes are Risen (RR) Whenever Lucy’s cake is Risen, Ricky’s cake tastes Good (RG) Whenever Ricky’s cake is Risen, Lucy’s cake tastes Good (GR)

quantum.info Entanglement: a culinary analogy Cakes prepared in pairs Q Cakes Inc. Baked on trips down two conveyor belts Lucy and Ricky find that 10% of the time both cakes are Risen (RR) Whenever Lucy’s cake is Risen, Ricky’s cake tastes Good (RG) Whenever Ricky’s cake is Risen, Lucy’s cake tastes Good (GR) How often do both Lucy and Ricky find that both cakes taste Good? (GG) Measure taste / taste 25% of time Therefore expect both Good = 25% x 10% = 2.5% (at least) If the cakes are entangled, then quantum mechanics predicts both cakes never taste Good! = 0% If the cakes are entangled, then quantum mechanics predicts both cakes never taste Good! = 0% This is Einstein’s hidden variable argument This is predicted by a version of Bell’s inequality

quantum.info Entanglement: the cake experiment US Patent R = -50.9˚ G = 0˚ (horizontal) F = 39.2˚ B = 90˚ (vertical) Photons entangled in polarisation We found that both cakes never tasted good If there is a hidden variable theory that describes the world, then it requires some faster-than-light aspects… Pretty sure… with 2 reasonable physical assumptions, probability of error is …00006% 3,233 zeroes

quantum.info In the last 100 years, industrial to information society: electronics industries— the diode photonics industries— the laser Quantum cryptography The Quantum Revolution Wave-particle duality Entanglement In a letter to his friend Conrad Habicht, Einstein called only one paper “very revolutionary” “...there is a Second Quantum Revolution coming — which will be responsible for most of the key physical technological advances for the 21st Century” Dowling & Milburn, Philosophical Transactions of the Royal Society of London A 361, 1655 (2003) Teleportation Quantum computation Quantum metrology In the last 10 years, >10,000 papers on Quantum Information Science More than he knew… quantum and relativity not quite compatible

quantum.info

Entanglement: a culinary analogy Lucy checks MeasRicky checks Meas 1 State RState F 2 Taste G 3 Taste B 4 State RTaste B 5 State R 6 State F 7 Taste G 8 Taste B 9 State RTaste B :.:. :. :.

quantum.info Quantum at UQ Astrophysics condensedmattertheory Einstein letter to UQ Prof. in Physics Museum

Quantum quest: the rise of quantum information Prof. Andrew White University of Queensland URL quantum.info

quantum.info Entanglement Term coined by Schrödinger in 1935 (better in German: Entwinement) Correlations between things that defy common sense Weird … needs an analogy …