Category Archives: Physics

PhD positions available

A fully-funded PhD position is available at the University of Technology Sydney, Australia, to conduct forefront theoretical research in the quantum information sciences, working with Dr Peter Rohde within the Centre for Quantum Software & Information (QSI).

The research topics are flexible, including:

* Quantum machine learning
* Quantum cryptography (especially homomorphic encryption and blind quantum computing)
* Quantum networking (especially cloud quantum computing)
* Quantum computing (with an emphasis on optical quantum computing, boson-sampling and quantum random walks)
* Quantum information theory
* Quantum metrology
* Your own suggestions for exciting projects in quantum technology

The candidate should have a background in physics, computer science, engineering, mathematics or a related discipline, and be highly creative, independent and passionate about quantum technology. The duration of the position is for 3 years, and includes a scholarship for $25,861/year (tax free). The position is research-only, with no teaching or coursework obligations.

QSI is a leading research centre in the quantum information sciences, and the candidate will have the opportunity to collaborate with leading researchers within the centre, as well as with other researchers domestically and internationally. Sydney is home to several major quantum research centres, presenting outstanding local collaboration opportunities.

The candidate will conduct theoretical research to be published in international journals, present research findings at major conferences, and build collaboration networks. Travel opportunities will be available.

To apply for the position or request further information, please contact Dr Peter Rohde ( by January 14. When applying, please provide a resume, academic record, contact details for two academic referees, and a statement of your research interests and passions. Applications are now open.

Please distribute this advert amongst your colleagues, students, mailing lists and Facebook groups.

– Ad astra per alas fideles. Scientia potentia est.

ARC Future Fellowship

I’m pleased and honoured to announce that I have just been awarded a prestigious ARC Future Fellowship to conduct a 4 year project into quantum networking and encrypted quantum computation. I will be based at the University of Technology Sydney, where I have received tenure as a Senior Lecturer. Ad astra.

New paper: Linear optical quantum metrology with single photons

Full text available here.

Quantum number-path entanglement is a resource for super-sensitive quantum metrology and in particular provides for sub-shotnoise or even Heisenberg-limited sensitivity. However, such number-path entanglement has thought to have been resource intensive to create in the first place — typically requiring either very strong nonlinearities, or nondeterministic preparation schemes with feed-forward, which are difficult to implement. Very recently, arising from the study of quantum random walks with multi-photon walkers, as well as the study of the computational complexity of passive linear optical interferometers fed with single-photon inputs, it has been shown that such passive linear optical devices generate a superexponentially large amount of number-path entanglement. A logical question to ask is whether this entanglement may be exploited for quantum metrology. We answer that question here in the affirmative by showing that a simple, passive, linear-optical interferometer — fed with only uncorrelated, single-photon inputs, coupled with simple, single-mode, disjoint photodetection — is capable of significantly beating the shotnoise limit. Our result implies a pathway forward to practical quantum metrology with readily available technology.

Introduction to Mathematica

An elementary introduction to Mathematica, aimed at complete beginners, including: algebraic manipulation, solving equations, complex numbers, linear algebra, functions, plotting, derivatives, integrals, solving differential equations, flow control, interactive graphics, and much more. All you need is Mathematica to try this out for yourself. I give several simple projects, including implementing a classical random walk, and basic quantum optics using operator algebra.

New paper: Sampling arbitrary photon-added or photon-subtracted squeezed states is in the same complexity class as boson sampling

Download full article here.

Boson sampling is a simple model for non-universal linear optics quantum computing using far fewer physical resources than universal schemes. An input state comprising vacuum and single photon states is fed through a Haar-random linear optics network and sampled at the output using coincidence photodetection. This problem is strongly believed to be classically hard to simulate. We show that an analogous procedure implements the same problem, using photon-added or -subtracted squeezed vacuum states (with arbitrary squeezing), where sampling at the output is performed via parity measurements. The equivalence is exact and independent of the squeezing parameter, and hence provides an entire class of new quantum states of light in the same complexity class as boson sampling.

New book chapter: An introduction to boson-sampling

Read the full article here.

Boson-sampling is a simplified model for quantum computing that may hold the key to implementing the first ever post-classical quantum computer. Boson-sampling is a non-universal quantum computer that is significantly more straightforward to build than any universal quantum computer proposed so far. We begin this chapter by motivating boson-sampling and discussing the history of linear optics quantum computing. We then summarize the boson-sampling formalism, discuss what a sampling problem is, explain why boson-sampling is easier than linear optics quantum computing, and discuss the Extended Church-Turing thesis. Next, sampling with other classes of quantum optical states is analyzed. Finally, we discuss the feasibility of building a boson-sampling device using existing technology.