- 1989-1994 Lecturer, Griffith University
- 1994-1995 Postdoctoral Research Fellow, Max Planck Society Workgroup on Nonclassical Light, Humboldt University, Berlin, Germany
- 1995-1997 Postdoctoral Research Assistant, The Open University, Milton Keynes, UK
- 1997-2000 Senior Lecturer, University of Hertfordshire, Hatfield, UK
- 2000-2005 Reader, University of Hertfordshire, Hatfield, UK
- 2004-2005 Leverhulme Trust Research Fellowship
- 2005-2010 Senior Lecturer, Griffith University
- 2011-....... Associate Professor, Griffith University
- What makes the universe tick?, by M. Brooks, 22 November 2008, page 32-35, New Scientist.
...In her analysis of this scenario, Vaccaro has found that a "present" quantum state of a neutral kaon is a billion times more similar to its future quantum state than its past quantum state. This means the present state is more likely to evolve into the future than the past. "The overall effect is like a random walk with a strong bias in one direction," Vaccaro says. "We may sometimes step backwards, but on average we are moving forwards in time...
- Scientists show how to erase information without using energy by L. Zyga, 25 January 2011, PhysOrg.
- Time flies when you're a subatomic particle – new quantum mechanics turns spacetime on its head by M. Atherton21 January 2016, International Business Times.
- The variable behavior of two subatomic particles, K and B mesons, appears to be responsible for making the universe move forwards in time, 28 January 2016, Reddit.
- Scientists May Have Just Figured Out Why Time Moves Forward, Not Backwards by A. Carpineti, 29 January 2016, IFL Science.
- A physicist has a new explanation for why time moves forwards, not backwards by F. Macdonald,1 February 2016,Science Alert.
- Why time only ever moves forward by R. O'Hare, 2 February 2016, Daily Mail.
- Scientist Figures Out Why Time Moves Forward And Not Backward by The Engineer, 3 February 2016, Wonderful Engineering.
- This New Theory Explains Why Time Only Moves Forwards by J. Kennell, 4 February 2016, The Science Explorer.
- One time or another: Our best 5 theories of the fourth dimension by Anil Ananthaswamy, 4 February 2017, New Scientist.
Wikipedia article references
- "Optical apparatus for implementing Schumacher's quantum data compression",
GB 2400252 A, 6 April 2005.
- "Quantum information source coding device and quantum information communication system",
Japan 3858067, 29 September 2006.
- "Quantum source coding apparatus and quantum information communication system",
US 07403713 B2, 22 July 2008 (2008).
- S.M. Barnett and J.A. Vaccaro, "The Quantum Phase Operator: A Review" (Taylor and Francis, London, 2007)
- Group theoretic formulation of complementarity, QCMC'06, Tsukuba, Japan, 28 November-3 December 2006
- Quantum Polling, CQCT Workshop, IMAX Centre, Sydney, 6-8 February 2007
- Quantum Illusions and Time, GUMPTION GU 10 August 2007
- Quantum Reference Systems, Relativistic Quantum Information Workshop, Customs House, Brisbane, 17 November 2007.
- Origin of the anthropocentric flow of time?, The Clock and the Quantum: Time and Quantum Foundations, Perimeter Institute of Theoretical Physics, Waterloo Canada, 28 September - 2 October, 2008
- The cost of information erasure in atomic and spin systems, The 8th Asian International Seminar on Atomic and Molecular Physics (AISAMP8), University of Western Australia, Perth, Australia, 24-28 November 2008.
- T violation, direction of time and general relativity, Relativistic Quantum Information Workshop, Customs House, Brisbane, 10-11 December 2009.
- Universe as a quantum computer: algorithm for the shortest path through time, Ninth Meeting of The Scottish Quantum Information Research Network (QUISCO), Glasgow, Scotland UK, 19 April 2010.
- Unidirectionality of time induced by T violation, Fifth International Workshop DICE2010, Castiglioncello, Italy, 13-17 September 2010.
- Erasure of information under conservation laws, Quantum Information and Foundations of Thermodynamics, ETH Zurich, Switzerland, 9-12 August 2011.
- Single reservoir heat engine: controlling the spin, Frontiers of Quantum and Mesoscopic Thermodynamics, Prague, Czech Republic, 29 July - 3 August 2013.
- Making sense of a time symmetric universe: time travelling in both directions, The Time Machine Factory: [Unspeakable, Speakable] on Time Travel,Turin, Italy, 25-28 October 2015.
- Unravelling the enigma of Time, New Scientist Instant Expert: The Quantum World, Sydney, Australia, 22 October 2016.
- Pegg-Fest Symposium: a celebration of the work of Prof David Pegg, FAA, FRSE
22 November 2007.
- Leverhulme Trust Research Fellowship, 1 September 2004 - 31 October 2005.
- British Council Travel Grant, 14-18 February 2005.
- Royal Society Travel Grant, 2-6 May 2005.
- Griffith University, Research Grant, 2009.
- Australian Research Council, Linkage Grant 2014-2017.
Lists of Publications
A complete list of my publications can be found at the following websites:
- Publications (refereed): 74
- Citations (Web of Science): 1623
- h-index (Web of Science): 23
Publications by Research Topic
Quantum states of light - squeezing
- Amplifying squeezing light
- J.A. Vaccaro and D.T. Pegg, "Squeezing of light by coherent attenuation", Optica Acta, 33, 1141-1147 (1986);
- D.T. Pegg and J.A. Vaccaro,"Squeezing in the output of a high-gain atomic light amplifier", Optics Commun., 61, 317-320, (1987);
- J.A. Vaccaro and D.T. Pegg, "Squeezed atomic light amplifiers", J. Mod. Optics, 34, 855-872 (1987).
- Phase properties
- J.A. Vaccaro and D.T. Pegg, "Phase properties of squeezed states of light", Optics Commun. 70, 529-534 (1989);
- J.A. Vaccaro and D.T. Pegg, "Phase properties of optical linear-amplifiers", Phys. Rev. A, 49, 4985-4995 (1994);
- J.A. Vaccaro and D.T. Pegg, "Nondiffusive phase dynamics from linear-amplifiers and attenuators in the weak-field regime", J. Mod. Optics 41, 1079-1086 (1994);
- J.A. Vaccaro, S.M. Barnett and D.T. Pegg, "Phase fluctuations and squeezing", J. Mod. Optics 39, 603-614 (1992).
Pegg-Barnett Quantum Phase Operator
- Minimum uncertainty states
- J.A. Vaccaro and D.T. Pegg, "Physical number phase intelligent and minimum-uncertainty states of light", J. Mod. Optics 37, 17-29 (1990).
- Generalized canonical observables
- D.T. Pegg, J.A. Vaccaro and S.M. Barnett, "Quantum-optical phase and canonical conjugation", J. Mod. Optics 37, 1703 (1990).
- Mathematical formalism
- U. Leonhardt, J.A. Vaccaro, B. Bohmer and H. Paul, "Canonical and measured phase distributions", Phys. Rev. A 51, 84-95 (1995);
- J.A. Vaccaro, "Phase operators on Hilbert-space", Phys. Rev. A 51, 3309-3317 (1995);
- J.A. Vaccaro and R.F. Bonner, "Pegg-Barnett phase operators of infinite rank", Phys. Lett. A, 198, 167-174 (1995);
- J.A. Vaccaro and Y. Benaryeh, "Antinormally ordering of phase operators and the algebra of weak limits", Optics Commun., 113, 427-432 (1995).
- Wigner function for photon number and phase
- J.A. Vaccaro and D.T. Pegg, "Wigner function for number and phase", Phys. Rev. A 41, 5156-5163 (1990);
- J. Vaccaro, "Number-phase Wigner function on Fock space", Phys. Rev. A 52, 3474-3488 (1995);
- J.A. Vaccaro, "New Wigner function for number and phase", Optics Commun. 113, 421-426 (1995).
- General aspects of phase
- J.A. Vaccaro and D.T. Pegg, "On measuring extremely small phase fluctuations", Optics Commun. 105, 335-340 (1994);
- J.A. Vaccaro and D.T. Pegg, "Consistency of quantum descriptions of phase", Physica Scripta T48, 22-28 (1993);
- J.A. Vaccaro and A. Orlowski, "Phase properties of Kerr media via variance and entropy as measures of uncertainty", Phys. Rev. A 51, 4172-4180 (1995);
- A.R. Gonzalez, J.A. Vaccaro and S.M. Barnett, "Entropic uncertainty relations for canonically conjugate operators", Phys. Lett. A 205, 247-254 (1995).
- Bell correlations and the Wigner function
- U. Leonhardt and J.A. Vaccaro, "Bell correlations in phase-space - application to quantum optics", J. Mod. Optics, 42, 939-943 (1995).
Quantum state determination
- Reconstructing the wave function
- J.A. Vaccaro and S.M. Barnett, "Reconstructing the wave-function in quantum optics", J. Mod. Optics, 42, 2165-2171 (1995);
- O. Steuernagel and J.A. Vaccaro, "Reconstructing the density operator via simple projectors", Phys. Rev. Lett. 75, 3201-3205 (1995) [arXiv:quant-ph/9510014].
Stochastic Schrödinger equations
- From quantum jumps to quantum state diffusion
- J.A. Vaccaro and D. Richards, "Stochastic Schrodinger equations for optical fields based on atom detection", Phys. Rev. A., 58 2690-2698 (1998).
Electromagnetically-induced transparency (EIT)
- Transient EIT
- H.X. Chen, A.V. Durrant, J.P. Marangos, and J.A. Vaccaro, "Observation of transient electromagnetically induced transparency in a rubidium Lambda system", Phys. Rev. A 58 1545-1548 (1998);
- S.R. de Echaniz, A.D. Greentree, A.V. Durrant, D.M. Segal, J.P. Marangos and J.A. Vaccaro, "Observation of transient gain without population inversion in a laser-cooled rubidium Lambda system", Phys. Rev. A 64 055801 (2001);
- A.D. Greentree, T.B. Smith, S.R. de Echaniz, A.V. Durrant, J.P. Marangos, D.M. Segal and J.A. Vaccaro, "Resonant and off-resonant transients in electromagnetically induced transparency: Turn-on and turn-off dynamics", Phys. Rev. A 65, 053802 (2002) [arXiv:quant-ph/0109090].
- Hyperfine sublevels in laser cooled samples
- A.V. Durrant, H.X. Chen, S.A. Hopkins, and J.A. Vaccaro, "Zeeman-coherence-induced transparency and gain without inversion in laser-cooled rubidium", Optics Commun., 151, 135-146 (1998).
- 4 and 5 level systems
- A.D. Greentree, J.A. Vaccaro, S.R. de Echaniz, A.V. Durrant and J.P. Marangos, "Prospects for photon blockade in four-level systems in the N configuration with more than one atom",Journal of Optics B 2, 252-259 (2000) [ arXiv:quant-ph/0002091] ;
- S.R. de Echaniz, A.D. Greentree, A.V. Durrant, D.M. Segal, J.P. Marangos and J.A. Vaccaro, "Observations of a doubly driven V system probed to a fourth level in laser-cooled rubidium", Phys Rev. A 64, 013812 (2001) [arXiv:quant-ph/0102098];
- A.D. Greentree, D. Richards, J.A. Vaccaro, A.V. Durrant, S.R. de Echaniz, D.M. Segal and J.P. Marangos, "Intensity-dependent dispersion under conditions of electromagnetically induced transparency in coherently prepared multistate atoms", Phys Rev. A 67, 023818 (2002) [ arXiv:quant-ph/0209067 ].
- Vector model of EIT
- J.A. Vaccaro, A.V. Durrant, D. Richards, S.A. Hopkins, H.X. Chen and K.E. Hill, "Stochastic wavefunction diagrams for electromagnetically induced transparency, inversionless gain and shelving", J. Mod. Optics 45, 315-333 (1998).
Quantum Information Processing
- Classical properties of quantum gates
- J.A. Vaccaro, O. Steuernagel and S.F. Huelga, "A class of symmetric controlled quantum operations", J. Phys. A 34, 7057 (2001) [arXiv:quant-ph/0102015].
- Quantum remote control
- S.F. Huelga, J.A. Vaccaro, A. Chefles and M.B. Plenio, "Quantum remote control: Teleportation of unitary operations", Phys. Rev. A, 63 042303 (2001) [arXiv:quant-ph/0005061];
- S.F. Huelga, M.B. Plenio and J.A. Vaccaro, "Remote control of restricted sets of operations: Teleportation of angles", Phys. Rev. A 65, 042316 (2002) [arXiv:quant-ph/0101110].
- Quantum voting
- J.A. Vaccaro, J. Spring and A. Chefles, "Quantum protocols for anonymous voting and surveying", Phys. Rev. A 75, 012333 (2007) [arXiv:quant-ph/0504161].
- Quantum source coding (data compression)
- Y. Mitsumori, J.A. Vaccaro, S.M. Barnett, E. Andersson, A. Hasegawa, M. Takeoka and M. Sasaki, "Experimental demonstration of quantum source coding", Phys. Rev. Lett. 91, 217902 (2003) [arXiv:quant-ph/0304036];
GB Patent 2400252 A, 6 April 2005, Japan Patent 3858067, 29 September 2006, US Patent 07403713 B2, 22 July 2008.
- Y. Mitsumori, J.A. Vaccaro, S.M. Barnett, E. Andersson, A. Hasegawa, M. Takeoka and M. Sasaki, "Experimental demonstration of quantum source coding", Phys. Rev. Lett. 91, 217902 (2003) [arXiv:quant-ph/0304036];
Robust states of open quantum systems
- Quantum state of Bose-Einstein condensates and atom lasers
- S.M. Barnett, K. Burnett and J.A. Vaccaro, "Why a condensate can be thought of as having a definite phase", Journal of Research of the National Institute of Standards and Technology 101, 593 (1996);
- H.M. Wiseman and J.A. Vaccaro, "Atom lasers, coherent states, and coherence. I. Physically realizable ensembles of pure states", Phys. Rev. A 65, 043605 (2002) [arXiv:quant-ph/9906125];
- H.M. Wiseman and J.A. Vaccaro, "Atom lasers, coherent states, and coherence II. Maximally robust ensembles of pure states", Phys. Rev. A 65, 043606 (2002) [arXiv:quant-ph/0112145].
- Robust states as the preferred ensemble
- H.M. Wiseman and J.A. Vaccaro, "Maximally Robust Unravelings of Quantum Master Equations", Phys. Lett. A 250, 241-248 (1998) [arXiv:quant-ph/9709014];
- H.M. Wiseman and J.A. Vaccaro, "Inequivalence of pure state ensembles for open quantum systems: The preferred ensembles are those that are physically realizable", Phys. Rev. Lett. 87, 240402 (2001) [arXiv:quant-ph/0112115].
Superselection Rules, Reference Systems and Entanglement
- Effect on quantum entanglement
- H.M. Wiseman and J.A. Vaccaro, "Entanglement of indistinguishable particles shared between two parties" Phys. Rev. Lett. 91, 097902 (2003) [arXiv:quant-ph/0210002];
- J.A. Vaccaro, F. Amselmi and H.M. Wiseman, "Entanglement of identical particles and reference phase uncertainty", Int. J. Quant. Inf. 1, 427 (2003) [arXiv:quant-ph/0311028].
- Reference Ability
- S.J. Jones, H.M. Wiseman, S.D. Bartlett, J.A. Vaccaro and D.T. Pope, "Entanglement and symmetry: A case study in superselection rules, reference frames, and beyond" Phys. Rev. A 74, 062313 (2006) [arXiv:quant-ph/0608056];
- J.A. Vaccaro, F. Amselmi, H.M. Wiseman and K. Jacobs, "Trade off between the locally extractable work, accessible entanglement and local reference frame ability for bipartite systems", Phys. Rev. A 77, 032114 (2008) [arXiv:quant-ph/0501121];
- G. White, J.A. Vaccaro and H.M. Wiseman, "The consumption of reference resources", AIP Conference Proceedings 1110, 11-22 (2009) [arXiv:0811.3660].
- Optimal reference states
- G. White, J.A. Vaccaro and H.M. Wiseman, "Optimal reference states for maximum accessible entanglement under the local-particle-number superselection rule", Phys. Rev. A 79, 032109 (2009) [arXiv:0807.0064].
Particle-wave Duality and Complementarity
- Particle-wave duality
- J.A. Vaccaro, "Group Theoretic Formulation of Complementarity" Proceedings of the 8th International Conference on Quantum Communication, Measurement and Computing, Edited by O. Hirota et al. (NICT, Tokyo, 2006) [arXiv:1012.3532].
- J.A. Vaccaro, "Particle-wave duality: a dichotomy between symmetry and asymmetry", Proc. R. Soc. Lond. A 468, 1065-1084 (2012) [arXiv:1105.0083]
Foundations of Thermodynamics
- Information erasure without an energy cost
- J.A. Vaccaro and S.M. Barnett, "The cost of erasing information", AIP Conference Proceedings 1110, 37-40 (2009).
- J.A. Vaccaro and S.M. Barnett, "Information erasure without an energy cost", Proc. R. Soc. Lond. A 467, 1770-1778 (2011) [arXiv:1004.5330].
- S.M. Barnett and J.A. Vaccaro, "Beyond Landauer erasure", Entropy, 15, 4956-4968 (2013).
- T. Croucher, S. Bedkihal and J.A. Vaccaro, "Discrete Fluctuations in Memory Erasure without Energy Cost", Phys. Rev. Lett. 118, 060602 (2017).
Physical Nature of Time
- Unidirectionality of time
- J.A. Vaccaro, "Unidirectionality of time induced by T violation", J. Phys.: Conf. Ser. 306, 012057 (2011).
- J.A. Vaccaro, "T Violation and the Unidirectionality of Time", Found. Phys. 41, 1569-1596 (2011) [arXiv:0911.4528].
- J.A. Vaccaro, "T Violation and the Unidirectionality of Time: further details of the interference ", Found. Phys.45, 691-706 (2015) [arXiv:1503.06523].
- Origin of dynamics
- J.A. Vaccaro, "Quantum asymmetry between time and space", Proc. R. Soc. Lond. A 472, 20150670 (2016).
- J.A. Vaccaro,"An anomaly in space and time and the origin of dynamics", in S. Wuppuluri, G. Ghirardi Eds, "Space, Time and the Limits of Human Understanding" (Springer International, 2016) p 185-201.
Landauer argued that information is physical because the process of erasing the information stored in a memory device incurs an energy cost in the form of a minimum amount of mechanical work. We have recently found, however, that this energy cost can be reduced to zero by paying a cost in angular momentum or another conserved quantity. Erasing the memory of Maxwell's demon in this way implies that work can be extracted from a single thermal reservoir at a cost of angular momentum and an increase in total entropy. The new erasure mechanism calls for a fundamental restatement of the Second Law of thermodynamics [Proc. R. Soc. A 467, 1770-1778 (2011), eprint arXiv:1004.5330 , Entropy 15, 4956-4968 (2013) ]. It also imposes new restrictions for perpetual machines of the second kind. We have examined the nature of the discrete fluctuations in the cost of erasing information using spin angular momentum [Phys. Rev. Lett. 118, 060602 (2017)]. We are currently exploring experimental implementations of the erasure protocol.
Further information: see the Centre for Quantum Dynamics entry on Quantum Thermodynamics.
The quantum nature of time
Time reversal invariance (T) refers to the symmetry between the past and future. All physical processes obey this invariance. The one exception is the weak force in the decay of K and B mesons. The violation of T symmetry in these systems signifies a fundamental asymmetry between the past and future. I have recently shown that processes which violate T symmetry induce destructive interference between different paths that the universe can take through time. This work resolves the long-standing problem of modeling the dynamics of T violation processes. It shows that T violation has previously unknown, large-scale physical effects and that these effects underlie the origin of the unidirectionality of time [Found. Phys. 41 1569-1596 (2011) DOI, eprint arxiv:0911.4528, Found. Phys. 45 , 691-706 (2015) DOI, eprint arXiv:1503.06523].
Current work is exploring the implications for the difference between space and time [Proc. R. Soc. Lond. A 472, 20150670 (2016) DOI , Book chapter DOI].
New Scientist included my quantum theory of time in the article "One time or another: Our best 5 theories of the fourth dimension" by Anil Ananthaswamy, 1 February 2017.
The nature of physical objects to have both particle and wave properties is one of the foundational elements of quantum theory. Essentially a particle-like state is represented by a narrow wave function which is displaced by spatial translations. In contrast a wave-like state is represented by a spread out wave function which is invariant to spatial translations. The wave-particle dichotomy can therefore be seen as a competition between displacement and invariance of the state with respect to spatial translations. We have generalised this dichotomy to arbitrary quantum systems with finite dimensional Hilbert spaces as follows. We use arbitrary finite symmetry groups to represent transformations of the quantum system. The symmetry (i.e. invariance) or asymmetry (i.e. displacement) of a given state with respect to transformations of the group are identified with the generalised wave and particle nature, respectively. We adopt a measure of wave and particle properties based on the amount of information that can be encoded in the symmetric and asymmetric parts of the state [Proc. R. Soc. A 468, 1065-1084 (2012) DOI, eprint arXiv:1105.0083].
Quantum reference frames and entanglement
Our description of physical objects is always relative to reference frames of some sort. For example, the position of a car on campus might be "in the third car park from the main entrance of East Car Park". For this description to make sense we need to know where East Car Park is. Presumably its position is known with respect to the campus site etc. Likewise a description of a quantum system, in the form of a quantum state, is relative to a number of implicit references which are represented by other physical systems. Often the reference systems are large and can be treated as classical. For example, if a spin-1/2 particle is described as being in the "spin-up" state it is presumed that the direction of the positive z-axis ("up") is known, perhaps relative to the orientation of a string bob. However when we include the reference systems in the full quantum description we find that matters change. In particular, the clarity of the description of quantum systems depends on the 'size' of the accompanying quantum references. This has an impact when high-fidelity quantum states are needed in areas such as quantum computing. We are exploring the optimum states for quantum references and the effects on quantum entanglement. [See e.g. Phys. Rev. A 77, 032114 (2008), eprint arxiv:quant-ph/0501121; Phys. Rev. A 79, 032109 (2008), eprint arxiv:0807.0064].
Quantum data security
Data security is a major issue in everyday life, from electronic fund transfers to voting in an election. A revolution has occurred relatively recently in this field with advent of quantum information science. This new branch of research uses the quantum nature of physical systems as a basis for security. A range of applications have been developed such as quantum secret sharing, quantum data hiding, quantum anonymous transfer, quantum oblivious transfer, quantum broadcast communication, quantum identity authentication, quantum finger printing, quantum seals, quantum signatures and quantum exams. We recently introduced a secure protocol for voting (quantum voting) in elections where the privacy of the vote and the anonymity of the voter is protected by quantum physics [Phys. Rev. A 75, 012333 (2007), eprint arxiv:quant-ph/0504161]. A vote is made by performing an operation at one site, a voting booth if you will, but the information of the vote cannot be accessed from that site alone. This effect is spontaneous and due to the entangled nature of the quantum states used. Areas of interest include exploring how quantum physics beats classical systems in data security, examining the robustness of particular applications and examining security-anonymity trade offs.
- Group Theory
- Tensor Calculus
- Particle Physics
- Classical Physics: Lagrange and Hamilton formalisms
- Quantum Physics: mathematical formalism, quantum information basics
- Physics of Time
Griffith Experts gives further information regarding Joan's profile as generated from internal records at Griffith University:
More information, including personal opinions, appreciation of surreal art, description of a quantum computer and so on, can be found on Joan's personal homepage: