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QSCITECH PhD and MSc Scholarships and projects

At QSCITECH we have a vibrant environment for scientific training – with many opportunities and activities to train to excel at the highest international levels. Students have available to them potential MRes, PhD scholarships, their own travel/research budget (PhD), weekly seminars and regular journal clubs. Below we list possible PhD projects and interested MRes, PhD students/postdoctoral researchers should contact the relevant listed academic for opportunities surrounding a particular PhD project.

MRes Opportunities: Macquarie University provides a unique Master of Research with one year coursework and one year research. Funding is available to support students during their MRes studies and entry into Year 2 of the MRes to focus on research alone is encouraged – particularly for international students wishing to progress to a PhD. Applications are primarily due Oct & March each year. Current MRes research projects can be viewed here.

PhD Opportunities: Macquarie University provides a very generous PhD scholarship for 3 year PhD studies. These are quite competitive and applications must be made each year before Aug 31.

To apply for MRes/PhD studies in quantum science and technology first choose a suitable PhD project below and send your CV/Resume/undergraduate/postgraduate transcript to the associated academic supervisor – Subject: MRes/PhD Studies Application.

More information on the Pathway to a Research degree for Domestic and International candidates can be found on the Research Training website.

We are currently offering the following PhD projects:

Quantum Simulations 

A/Prof Gavin Brennen: Macquarie University

One of the great promises of quantum science is to simulate complex physical systems that are difficult to compute on classical machines. However, individual quantum systems are very fragile and to be useful in quantum devices for simulation, they must be accurately controlled. In the standard approach one must develop technology capable of controlling each and every individual quantum system within the device. The challenge of scaling up these control solutions to quantum devices containing hundred and perhaps millions of quantum systems seems incredibly daunting. We have shown how to run a quantum computer fault-tolerantly using semi-global operations and with very noisy measurements [1]. Here semi-global means the number of control modes (fields) is only very weakly dependent on the number of information carriers (specifically it scales logarithmically with the number of logical qubits) [2]. One project will study how apply these ideas to specific quantum simulation algorithms, particularly constant depth circuits and to compute a threshold on the individual gate errors. Another project will focus on how to use low depth quantum circuits to compute partition functions [3] for Lagrangians particularly in the context of continuous variable encodings using photonic networks. A third project will investigate analogue [4] and digital simulations of quantum field theories [5].

[1] G.A. Paz-Silva, G.K. Brennen, and J. Twamley, Fault Tolerance with Noisy and Slow Measurements and Preparation, Phys. Rev. Lett. 105, 100501 (2010). 

[2] G.A. Paz-Silva, G.K. Brennen, and J. Twamley, Bulk Fault Tolerant Quantum Information Processing with Boundary Addressability, New J. Phys. 13, 013011 (2011). 

[3] S. Iblisdir, M. Cirio, O. Boada, and G.K. Brennen, Low Depth Quantum Circuits for Ising Models, Annals of Physics 340, 205 (2014). 

[4] G.K. Brennen, G. Pupillo, E. Rico, T.M. Stace, and D. Vodola, "Loops and strings in a superconducting lattice gauge simulator," arXiv:1512.06565.

[5] G.K. Brennen, P. Rohde, B. Sanders, and S. Singh,  Multi-scale quantum simulation of quantum field theory using wavelets, Phys. Rev. A 92, 0323145 (2015); "Holographic construction of quantum field theory using wavlets," arXiv:1606.05068.

Topological Quantum Science 

A/Prof Gavin Brennen: Macquarie University

We traditionally classify order in many body systems through the lens of Landau theory where the symmetry at the microscopic level is broken to a lower symmetry in the ground states, e.g. ordering of spins along one direction in the Ising model. In topological systems the opposite occurs, the ground states have emergent symmetries not present in the microscopic equations of motion. Such emergent properties include (1) non-locally degrees of freedom that can be used to store quantum information in a protected way and (2) anyons which are particles in 2D which have richer behavior under exchange than Bosons or Fermions. One project will investigate how to engineer spin lattices using trapped atom/molecules/ or photonic networks which have topological order and emergent anyons [1,4].   Further we investigate how to make braiding operations for anyons fault tolerant in physical realisations and possible novel applications such as computing the statistics of braided systems [3].  Another project will study the statistical mechanics of these anyons via discrete time dynamics described by quantum walks and in continuous time via anyonic Hubbard models.  Numerical studies will include using and extended already developed code for anyonic matrix product states (MPS) [5].

[1] G. K. Brennen, M. Aguado, and J. I. Cirac. Simulations of quantum double models. New J. Phys., 11:053009 (2009).

[2] L. Lehman, V. Zatloukan, G.K. Brennen, J.K. Pachos, and Z. Wang, Quantum Walks with Non-Abelian Anyons, Phys. Rev. Lett. 106, 230404 (2011).

[3] V. Zatloukan, L. Lehman, J.K. Pachos, and G.K. Brennen Transport properties of anyons in random topological environments, Physical Review B 90, 134201 (2014).

[4] T. Demarie, T. Linjordet, N. Menicucci, and G.K. Brennen, Detecting Topological Entanglement Entropy in a Lattice of Quantum Harmonic Oscillators, New Journal of Physics 16, 085011 (2014).

[5]  S. Singh, R. Pfeifer, G. Vidal, and G.K. Brennen, Matrix Product States and Efficient Simulation of Anyons, Physical Review B 89, 075112 (2014); B.M. Ayeni, S. Singh, R.N.C. Pfeifer, G.K. Brennen, Simulation of braiding anyons using Matrix Product States, Phys. Rev. B 93, 165128 (2016).

Many Body Quantum Information

A/Prof Gavin Brennen: Macquarie University 

There are several models for quantum computation which are equivalent in ability to simulate each other but which differ in how they operate. For example, in the measurement based model one begins with a special resource state (a 2D lattice of entangled spins with one spatial axis representing position on the computational register, the other time) and then performs adaptive single spin measurements on the remaining correlated spins to process a quantum computation.  This project will investigating how to prepare and process good resource states which are stable ground states of naturally occuring systems--i.e. computational phases of matter [1,2]. The scope of the research covers: identifying stable computational phases of matter [3], how to use many body states as resources for precision measurement [4], and holographic encoding of boundary field theories using lifted tensor networks [5].

[1] G. K. Brennen and A. Miyake. Measurement-based quantum computer in the gapped ground state of a two-body hamiltonian. Phys. Rev. Lett., 101(1):010502 (2008).

[2] A.S. Darmawan, G.K. Brennen, and S.D. Bartlett, Measurement-based quantum comptuation in a two dimensional phase of matter, New J. Phys. 14, 013023 (2012). 

[3] S.D. Bartlett, G.K. Brennen, A. Miyake, and J. Renes, Quantum Computational Renormalization in the Haldane Phase, Phys. Rev. Lett. 105, 110502 (2010). 

[4] S. Bartlett, G.K. Brennen, and A. Miyake, "Robust symmetry-protected metrology with the Haldane phase,' (QST to appear), arXiv:1608.08221.

[5] S. Singh, N.A. McMahon, and G.K. Brennen, "Holographic spin networks from tensor network states," arXiv:1702.00392.

Quantum Simulation of Quantum Chemistry

Berry Quantum Simulations PhD Scholarship Project

Dr. Dominic W Berry: Macquarie University
Prof. Alán Aspuru-Guzik: Harvard University

There are an enormous variety of technological challenges, such as renewable energy and pharmaceutical design, that could be solved if one could rapidly simulate molecules. The problem is that quantum systems are fundamentally difficult to simulate on normal “classical” computers. This led Feynman to propose the idea of quantum computers [1]. Later Lloyd gave a general quantum simulation algorithm [2], but it was Aspuru-Guzik and co-workers who showed how to simulate quantum chemistry on a quantum computer [3]. Unfortunately, this algorithm was relatively slow [4].

The goal of this PhD project is to develop techniques for quantum computers to simulate quantum chemistry that are much faster, and could enable quantum computers to simulate much larger molecules. The basic techniques to achieve this have been presented in a pair of papers by Berry and Aspuru-Guzik [5], and are based upon the ability to exponentially accelerate a numerical integral. This project will fully develop these techniques and devise ways to further improve the complexity, for example by showing how to better choose integration grids, and tailoring the algorithms for real molecules.

[1] R. Feynman, International Journal of Theoretical Physics 21, 467 (1982).
[2] S. Lloyd, Science 273, 1073 (1996).
[3] A. Aspuru-Guzik, A. D. Dutoi, P. J. Love, and M. Head-Gordon, Science 309, 1704 (2005).
[4] D. Wecker, B. Bauer, B. K. Clark, M. B. Hastings, and M. Troyer, Phys. Rev. A 90, 022305 (2014).
[5] R. Babbush, D. W. Berry, I. D. Kivlichan, A. Y. Wei, P. J. Love, and A. Aspuru-Guzik, arXiv:1506.01020; arXiv:1506.01029 (2015).

Optical trapping and Levitation of nanoparticles

Molina-Terriza Quantum Levitation PhD MSc Scholarship Project

A/Prof Thomas Volz: Macquarie University
Prof. Jason Twamley: Macquarie University

External collaborators: Prof. Gabriel Molina Terriza and Dr Mathieu Juan

*thomas.volz@mq.edu.au

In the Quantum Nanophotonics laboratories of Macquarie University, we have started a series of experiments showing that the the Physics of the Star Wars’ “tractor beam” was possible. Using electromagnetic radiation (an optical beam) we have managed to capture a small particle and move it around without physically touching the particle. This technique, which has led to a Nobel prize in physics and a whole new industry in biotechnology, could allow us to explore new physical regimes when we combine it with cooling the particle to the its quantum ground state. Nevertheless, the possibility of trapping small particles in vacuum (optical levitation) is still a battleground for physicists.

In this project we will set-up an experiment to trap and manipulate small particles in water, air and vacuum. We will use a continuous wave laser and a nanopositioner in order to beat the gravitation and van der Waal’s forces locking the particles to the substrates. We will explore different experimental techniques to increase the optical forces to levitate smaller and smaller dielectric particles.

This project is part of an ambitious project to observe quantum effects in dielectric particles, by isolating them from any decoherence due to the environment. Over a 3 year PhD program, the candidate will have the opportunity to use these techniques to cool the dielectric particle to ultralow temperatures and observe the quantum properties of a macroscopic object.

[1] Near-field Levitated Quantum Optomechanics with Nanodiamonds: Strong Single-Photon Coupling at Room Temperature arXiv:1505.03363

Quantum logic in colour

Steel PhD Scholarship Project on quantum optics in frequency and time

Prof. Michael Steel: Macquarie University

In quantum mechanics, interference occurs whenever a given experimental outcome can come about in two or more ways. This means for instance that two photons incident from opposite sides of an oblique two-way mirror always leave as a pair. Weirdly, the two photons need not even reach the mirror at the same time: the interference occurs as long as we can’t tell which one arrived first. This surprising phenomenon is at the heart of photonic approaches to quantum information processing, including including quantum metrology, boson sampling, and optical quantum computing. These operations have been thoroughly investigated in real space, but there are even stranger analogs which are much less studied: it should be possible to see interference of two photons of completely different colour.

In this project we will explore the description and design of quantum logic gates and processes in the frequency and time domains. We will design nonlinear optical devices that enable the quantum interference of photons of different frequencies, including the optimisation and suppression of competing frequency conversion processes. Connections to classical optics will be pursued to facilitate ease of laboratory characterisation and implementation. There will be close interaction with experimental teams working on these and similar ideas.
Z. Chaboyer, T. Meany, L. G. Helt, M. J. Withford, and M. J. Steel, Tunable quantum interference in a 3D integrated circuit Scientific Reports 5, 9601:1–5 (2015)

L. G. Helt, J. E. Sipe, and M. J. Steel, Spontaneous parametric downconversion in waveguides: What’s loss got to do with it? New Journal of Physics 17, 013055:1–17 (2015)

M. J. Collins, C. Xiong, I. H. Rey, T. D. Vo, J. He, S. Shahnia, C. Reardon, T. F. Krauss, M. J. Steel, A. S. Clark, and B. J. Eggleton, Integrated spatial multiplexing of heralded single photon sources Nature Communications 4, 2582:1–7 (2013)

M. K. Dezfouli, M. J. Steel, J. E. Sipe and M. M. Dignam, Heisenberg treatment of pair-generation in lossy coupled-cavity systems Physical Review A 90, 043832:1–12 (2014)

Single Spin Sensing with Nano Diamonds

Single spin sensing PhD project in the Volz group.

Dr Thomas Volz*: Macquarie University
Dr Sarah Kaiser: Macquarie University

*thomas.volz@mq.edu.au

The Quantum Materials and Applications group at Macquarie University Sydney is looking for an interested and highly motivated individual to work on a PhD project on nanoscale single-spin sensing with defect centres in (nano-)diamonds. The technique of using single NV centres for magnetic field sensing down to the nT/sqrt(Hz) level in different contexts is well established in the field and has been applied to different scenarios including magnetic-field sensing in biological contexts [1]. This project aims at implementing a low-temperature single-spin sensing platform based on a closed-cycle cryostat and a commercially available AFM platform. The platform will be used for studying novel and exotic solid-state materials and for exploring their potential for real-world applications. The student should bring a strong interest in technology and a good understanding and working knowledge of quantum mechanics. Previous experience in the field is a plus but not absolutely necessary.

If you are interested in the project please contact Dr Thomas Volz (thomas.volz@mq.edu.au) and/or Dr Carlo Bradac (carlo.bradac@mq.edu.au).

[1] L. Rondin, J.-P. Tetienne, T. Hingant, J.-F. Roch, P. Maletinsky, and V. Jacques Magnetometry with nitrogen-vacancy defects in diamond Rep. Prog. Phys. 77, 056503 (2014)

Numerical Techniques for Long-Range Hamiltonians

Pfeifer PhD Scholarship Project on Numerical Techniques for Long-Range Hamiltonians

Dr. Robert Pfeifer, robert.pfeifer@mq.edu.au
Prof. Jason Twamley, jason.twamley@mq.edu.au

Tensor network algorithms are some of the most powerful general techniques ever developed for the study of low-dimensional quantum systems. However, the study of systems with long-range (polynomial) interactions remains challenging, and existing algorithms either specialise to short-range interactions (e.g. MERA [1]) or introduce an effective cut-off (e.g. DMRG with MPO [2]). Almost all physical systems exhibit polynomial interactions and to explore novel quantum correlations mediated by such long range interactions has so far proved feasible only in relatively small systems. In quantum computers, many types of quantum error correction typically do not correct errors due to long range interactions and so its important to be able to gauge how such interactions can build up large correlations in the various quantum systems upon which quantum computers are based.

In this project, you will work to develop a real-space tensor network algorithm for large spin systems with polynomial interactions. You will acquire skills and experience in the design and implementation of tensor network algorithms, and in the application of ideas in real-space renormalisation group theory to lattice systems [3]. You will then take these powerful methods and apply them to various detailed physical systems relevant to quantum information processing [4,5]. There is also the potential to collaborate with experimental groups to probe the accuracy of the simulations from an experimental point of view. Subject to interest, there may also be opportunities to work with anyonic systems, and to investigate the role of self-organisation in the design of tensor network algorithms.

Parity-Time symmetry phase transitions in quantum opto-acoustic systems

msteel_twamley_parity

A/Prof Michael Steel, michael.steel@mq.edu.au
Prof. Jason Twamley, jason.twamley@mq.edu.au

Conventional quantum mechanics of isolated systems is built upon the assumption of a Hermitian Hamiltonian to ensure physical real-valued energy levels. Parity-Time symmetric (PT) quantum systems are attracting enormous interest in the community. PT systems, while not Hermitian, still exhibit real eigenenergies and display complex and interesting behaviors. In particular such systems support a discontinuous phase transition when a control parameter is varied and PT symmetry is broken. Surprisingly, PT-symmetry breaking enables potentially very useful properties for technologies eg. non-reciprocal optical devices [1], enhancement of optomechanical coupling [2], and phonon/photon enhanced couplings.

In this project, we will explore the novel phase transitions that appear in PT related materials and in particular in systems that couple light to elastic vibrations (phononics) [4,5], and also to spin (spintronics). Such systems will have many potential applications ranging from novel types of sensors through to the quenching of quantum phase transitions. During the project you will learn techniques (analytic and numeric), in advanced photonics and acoustics, techniques related to quantum spin physics and the design and simulation of ultra-precise sensors [3].

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