The ARC Centre of Excellence for Engineered Quantum Systems

EQuS is an Australian Research Centre of Excellence grouping some of the best known Australian physicists to unravel the mysteries of the quantum world. EQuS has five nodes all around Australia so you can chose to live in sunny Brisbane, bustling Sydney, or beautiful Perth. Through focussed and visionary research EQuS will deliver new scientific insights and fundamentally new technical capabilities across a range of disciplines. Impacts of this work will improve the lives of Australians and people all over the world by producing breakthroughs in physics, engineering, chemistry, biology and medicine.

The primary goals of EQuS are to

  • Establish a world-leading research community driving the development of quantum technologies, with Australia as the focus of international efforts.
  • Stimulate the Australian scientific and engineering communities to exploit quantum devices and quantum coherence in next-generation technologies.
  • Train a generation of young scientists with the skills needed to lead the future of technology development.
  • Demonstrate the potential and capabilities of engineered quantum technologies by realizing technological breakthroughs in novel and useful engineered quantum coherent systems.
  • Create a design methodology supporting the development of all new technologies for the Quantum Era.

For more details see http://equs.org/

We experimentally realize a quantum random number generator (QRNG) with randomness of each generated number certified by the Kochen-Specker theorem. Employing this novel certification scheme eliminates the necessity for input seed random numbers and lifts the non-locality requirement for the certified QRNG. Implementation on the base of superconducting qubits allows achieving a bit rate of 25 kBit/s, two orders of magnitude higher than previously reported certified QRNGs. These improvements make our result a major step towards realization a practical certified quantum QRNG with implications for digital security and modelling algorithms.

Jerger M., Vasselin Z. and Fedorov A., 2017
arXiv:1706.05829

We present a technique to measure the transfer function of a control line using a qubit as a vector network analyzer. Our method requires coupling the line under test to the the longitudinal component of the Hamiltonian of the qubit and the ability to induce Rabi oscillations through simultaneous driving of the transversal component. We used this technique to characterize the 'flux' control of a superconducting Transmon qubit in the range of 8 to 400\,MHz. Our method can be used for the qubit 'flux' line calibration to increase the fidelity of entangling gates for the quantum processor. The qubit can be also used as a microscopic probe of the electro-magnetic fields on a chip. 

The ability to determine whether a multi-level quantum system is in a certain state while preserving quantum coherence between all orthorgonal states is necessary to realize binary-outcome compatible measurements which are, in turn, a prerequisite for testing the contextuality of quantum mechanics. In this paper, we use a three-level superconducting system (a qutrit) coupled to a microwave cavity to explore different regimes of quantum measurement. In particular, we engineer the dispersive shifts of the cavity frequency to be identical for the first and second excited states of the qutrit which allows us to realize a strong projective binary-outcome measurement onto its ground state with a fidelity of 94.3%. Complemented with standard microwave control and low-noise parametric amplification, this scheme can be used to create sets of compatible measurements to reveal the contextual nature of superconducting circuits. 

Reshitnyk Y., Jerger M. and Fedorov A., 2016
EPJ Quantum Technol., 3, 1, pp. 1-6

Three-dimensional (3D) microwave cavities with embedded superconducting quantum bits (qubits), provide a popular and versatile platform for quantum information processing and hybrid quantum systems. A current issue that has arisen is that 3D superconducting cavities do not permit magnetic field control of qubits embedded in these cavities. In contrast, microwave cavities made of normal metals can be transparent to magnetic fields, but experience a much lower quality factor, which negates many of the advantages of the 3D architecture. Here we presented measurements of a device that bridges a gap between these two types of cavities with magnetic field control and an order of magnitude higher quality factor compared to all previously tested copper cavities. An added benefit to that our hybrid cavity possesses is that it also provides an improved thermal link to the sample that superconducting cavities alone cannot provide. A large improvement in quality factor and magnetic field control makes this 3D hybrid cavity an attractive new platform for circuit quantum electrodynamics experiments.

Jerger M. et al, 2016
Nature Communications, 7, pp. 12930

Contextuality is one of the most fundamental properties of quantum mechanics, distinguishing it from classical physics without a need for nonlocality or entanglement. It is also a critical resource for exponential speedup in universal surface-code quantum computing. Our result is the first experiment violating a noncontextuality inequality with an indivisible system where entanglement cannot be defined which also addresses all known major loopholes, such as the detection, compatibility and individual-existence loopholes. Violating noncontextuality with superconducting circuits, a leading candidate for implementing surface-code quantum computing, comprises an important conceptual milestone in demonstrating their suitability for quantum technological applications.

We discuss a similarity between resonant oscillations in two nonlinear systems; namely, a chain 
of coupled Duffing oscillators and a bilayer fish-scale metamaterial. In such systems two

Macha Pascal et al, 2014
Nature Communications, 5, pp. 5146

Implementation of a quantum metamaterial using superconducting qubits