Physics is in the midst of the second quantum revolution

It's in this revolution in which we are using the truly weird and wonderful aspects of quantum theory—like Schrödinger’s cat and Heisenberg’s uncertainty principle—to create technological advancements in the 21st century.

At the same time there are still profound problems in physics—in particular how quantum theory can be reconciled with our experience of the macroscopic world and the physical nature of time—which we are trying to solve.

Quantum information theory

Quantum information theory is what lies behind emerging quantum technologies, such as quantum cryptography (with security guaranteed by the laws of physics) and quantum computing (which promises exponentially faster solutions to certain problems).

Our theoretical work at CQD takes place within the Australia-wide Centre for Quantum Computation and Communication Technology, and we work closely with the experimentalists in CQD’s quantum optics information laboratory. Topics of research include new forms of quantum information processing, quantum correlations, and quantum cryptography.

Team leaders

Recent key papers

  • Wollmann S. Walk N. Bennet A, Wiseman H. Pryde G, (2016), Observation of Genuine One-Way Einstein-Podolsky-Rosen Steering, Physical Review Letters 116, 160403
  • Fuwa M. Takeda S. Zwierz M. Wiseman H. Furusawa A, (2015), Experimental proof of nonlocal wave function collapse for a single particle using homodyne measurements, Nature Communications 6, 6665
  • Buscemi F. Hall M. Ozawa M. Wilde M, (2014), Noise and disturbance in quantum measurements: An information-theoretic approach. Physical Review Letters 112, 050401
  • Branciard C. Cavalcanti E. Walborn S. Scarani V.  Wiseman H, (2012), One-sided Device-Independent Quantum Key Distribution: Security, Feasibility and the Connection with Steering,  Physical Review Letters 85, 010301(R)

Key publications

  • Matthew S. Palsson, Mile Gu, Joseph Ho, Howard M. Wiseman, and Geoff J. Pryde (2016), Experimentally modelling stochastic processes with less memory by the use of a quantum processor, Science Adv. 3, e1601302
  • Fuwa M. Takeda S. Zwierz M. Wiseman H. Furusawa A (2015). Experimental proof of nonlocal wave function collapse for a single particle using homodyne measurements, Nature Communications 6, 6665
  • A.J. Bennet, D.A. Evans, D.J. Saunders, C. Branciard, E.G. Cavalcanti, H.M.Wiseman and G.J. Pryde (2012). Arbitrarily Loss-Tolerant Einstein-Podolsky-Rosen Steering Allowing a Demonstration over 1 km of Optical Fiber with No Detection Loophole, Physical Review X 2, 031003.
  • Branciard C. Cavalcanti E. Walborn S. Scarani V.  Wiseman H (2012). One-sided Device-Independent Quantum Key Distribution: Security, Feasibility and the Connection with Steering,  Physical Review A 85, 010301(R)

Quantum measurement and control theory

Unlike classical systems, measurement plays an essential role in quantum mechanics, as measuring a quantum system unavoidably disturbs it. This limits the precision with which one can estimate the parameters influencing a quantum system, and entangled states and adaptive (i.e. actively controlled) measurement schemes are typically necessary to attain these limits. However, measurements also allow systems to be controlled in uniquely quantum ways, enabling, for example, measurement-based quantum computation, and rapid state-preparation using measurement and feedback control.

We work across each of these topics, many in collaboration with experimental partners in the Centre for Quantum Computation and Communication Technology.

Team leaders

Recent key publications:

  • Guevara Prieto, I., & Wiseman, H. (2015). Quantum State Smoothing. Physical Review Letters, 115(18), 180407–1–180407–6.
  • Berry, D. W., Tsang, M., Hall, M., & Wiseman, H. (2015). Quantum Bell-Ziv-Zakai Bounds and Heisenberg Limits for Waveform Estimation. Physical Review X, 5, 031018–1–031018–28.
  • Yonezawa. H. et al. 2012. Quantum-enhanced optical phase tracking. Science 337, 1514–1517.
  • Wiseman, H., & Milburn, G. J. (2010). Quantum Measurement and Control. United Kingdom: Cambridge University Press.

Other key publications

  • Guevara I. Wiseman H, (2015), Quantum State Smoothing, Physical Review Letters 115, 180407
  • Berry D. Tsang M. Michael J. Hall W. Wiseman H, (2015), Quantum Bell-Ziv-Zakai bounds and Heisenberg limits for waveform estimation, Physical Review X 5, 031018
  • G. A. Paz-Silva and Lorenza Viola, (2014), General Transfer-Function Approach to Noise Filtering in Open-Loop
  • Quantum Control, Physical Review Letters 113, 250501.
  • H. Yonezawa H. et al. (including H. Wiseman as corresponding author), (2012), Quantum-enhanced optical phase tracking, Science 337, 1514–1517

Foundations and extensions of quantum theory

Quantum mechanics is our best theory of the microscopic world, yielding accurate statistical predictions.  However, significant issues remain to be resolved, including the limits to what can be known about a quantum system, what the theory implies for our understanding of reality, and whether it needs to be extended in some way to reconcile the Schrödinger equation with collapse of the wave function.

Topics of research include joint measurement uncertainty relations, a new many interacting worlds interpretation of quantum mechanics, the role of symmetry/asymmetry in wave-particle duality, axiomatic approaches to quantum mechanics and the quantum theory of time.

Team leaders

Key publications

  • Mahler D. Rozema L. Fisher K. Vermeyden L. Resch K. Wiseman H. Steinberg A, (2016), Experimental nonlocal and surreal Bohmian trajectories, Science Adv.2, e1501466
  • M. Ringbauer, B. Duffus, C. Branciard, E. G. Cavalcanti, A. G. White and A. Fedrizzi, (2015), Measurements on the
  • reality of the wavefunction, Nature Physics 11, 249.
  • Michael J. Hall W. Deckert D. Wiseman H, (2014), Quantum phenomena modelled by interactions between many classical worlds, Physical Review Letters 4, 041013
  • Hall, M., Deckert, D. A., & Wiseman, H. (2014), Quantum Phenomena Modeled by Interactions between Many Classical Worlds. Physical Review X, 4, 041013–1–041013–17.
  • Wiseman H, (2014), The Two Bell's Theorems of John Bell, Physical Review Letters 47, 424001 (Special Issue, 50 years of Bell's theorem).
  • Vaccaro J, (2016), Quantum asymmetry between time and space, Proceedings of the Royal Society A 472, 20150670 (2016).
  • Vaccaro J, (2015), T Violation and the Unidirectionality of Time: Further Details of the Interference, Found. Phys. 45, 691-706.
  • Vaccaro J, (2011), T Violation and the Unidirectionality of Time, Found. Phys. 41, 1569-1596

Quantum thermodynamics

Until recently, scientists have believed that erasing information requires energy. Our research shows that this energy cost can be reduced to zero and instead, the cost of erasure can be paid in terms of another conserved quantity, such as spin angular momentum.

The new erasure mechanism calls for a fundamental revision of thermodynamics, including the second law.  It also imposes new restrictions for perpetual machines of the second kind.

We are currently exploring experimental implementations and possible applications.

Team leader

Recent key papers

  • Croucher, T., Bedkihal, S. & Vaccaro, J. A. (2017). Discrete Fluctuations in Memory Erasure without Energy Cost. Phys. Rev. Lett. 118, 060602.
  • Barnett S. Vaccaro J, (2013), Beyond Landauer erasure, Entropy 15, 4956-4968
  • Vaccaro J. Barnett S, (2011), Information erasure without an energy cost, Proceedings of the Royal Society A 467, 1770-1778
  • Vaccaro J. Barnett S, (2009), The Cost of Erasing Information, AIP Conference Proceedings 1110, 37-40

Want to know more?

Contact the Centre for Quantum Dynamics