Topological quantum matters are useful for sensing

Akimasa Miyake has recently published in a new journal Quantum Science and Technology in collaboration with Stephen Bartlett (University of Sydney) and Gavin Brennen (Macquarie University), presenting a scheme of robust quantum sensing using one-dimensional strongly-interacting spin chains. It takes advantage of passive error-preventing properties of a symmetry-protected topologically ordered phase, to measure the direction and strength of an unknown electronic field.

The full article can be found online at Quantum Sci. Technol. 3, 014010 (2018) .

How can one verify the performance of a near-term quantum device?

Jacob Miller, Keith Sanders, and Akimasa Miyake have recently published a paper in Physical Review A presenting a distinctive means of demonstrating the unique computational power inherent in quantum mechanics. Their work follows other proposals in the growing topic of “quantum computational supremacy”, which aims to construct a realistic device implementing a sampling-based computational task which is otherwise impossible with any modern digital computer. Such sampling tasks must achieve a careful balance, where they are both easier to implement in a laboratory than full quantum computation, but must also be hard enough to require genuinely quantum effects to solve.
The proposal put forward by Miller, Sanders, and Miyake has several desirable features. First, it can carry out its computational task in a constant amount of time, helping to mitigate the harmful effects of experimental noise. Secondly, it is capable of seamlessly verifying the correct operation of the difficult sampling task with exactly the same resources required to perform the sampling itself. This latter property is important, since the difficulty of the sampling generally makes it extremely hard to check whether or not a realistic device is actually achieving quantum supremacy. While previous works had satisfied one or the other of these properties, the current proposal uses the framework of measurement-based quantum computation and insights from the study of quantum phases of matter to simultaneously achieve both.
The full article can be found online at Phys. Rev. A 96, 062320 (2017).

(a) Quantum circuit to sample probability distributions related to certain Boolean functions. The task is expected to be intractable to modern computers. (b) Our measurement-based implementation, which realizes a sampling task and its verification procedure under the same resource requirement.

Visiting Doctoral Scholars

CQuIC welcomes Mariami (Mari) Gachechiladze and Davide Orsucci, Visiting Scholars who will be hosted by Professor Akimasa Miyake at CQuIC for the next three months.

Mari Gachechiladze is a Ph.D. student in Professor Otfried Guehne’s group at the University of Siegen in Germany, and working in theoretical quantum optics and quantum information.  Mari hopes to work on projects involving quantum computation with hypergraph states.

Davide Orsucci is a Ph.D. student in Professor Hans Briegel’s group at the University of Innsbruck in Austria.   He has been working on various projects, including quantum metrology, quantum error correction, and machine learning.  Davide is interested in extending his understanding and experience in quantum metrology and computation.



Congratulations to CQuIC Ph.D. Graduate, Jacob Miller

CQuIC PhD student Jacob Miller defended his PhD dissertation on May 3, 2017 and has completed all the requirements to be awarded a PhD in Physics. Jacob’s dissertation, entitled Measurement-Based Quantum Computation and Symmetry-Protected Topological Order, was supervised by Akimasa Miyake, for whom this is also a milestone, as Jacob is Akimasa’s first PhD student. Congratulations to both Jacob and Akimasa! We look forward to further great things from both of them.