CQT Talk by Low Pei Jiang, IQC, University of Waterloo

Title: Qudit Quantum Computing With Trapped Barium Ions  
Date/Time: 16-Aug, 02:00PM
Venue: Level 3 Seminar Room

Abstract: The finite number of trapped ions with full coherent control for quantum computing per ion trap is a practical limitation known to the ion trapping community. To scale up the computational Hilbert space with this physical limitation, encoding more computational states per trapped ion (i.e. qudit) is an attractive avenue. The metastable D-5/2 states of barium ions present several functionalities that are useful for qudit quantum computing. Using the S-1/2 to D-5/2 quadrupole transition of a barium ion, the metastable D-5/2 states can be utilized as shelved states necessary for qudit measurements or as computational states. In this presentation, I present our recent progress with experimental manipulations of these states. They include spectroscopy of the D-5/2 states, other utilities of the D-5/2 states such as ion cooling and micromotion detection, and state preparation and measurement (SPAM) of a 6-level qudit system. I also present our plan and progress towards a potentially record-breaking trapped ion qudit encoding with 137Ba+ ions. 

CQT Talk by Huang Zixin, Macquarie University

Title: Sub-wavelength quantumimaging and hypothesis testing for astronomy
Date/Time: 17-Aug, 02:00PM
Venue: Level 3 Seminar Room

Abstract: The resolution limit of standard imaging techniques is expressed by theRayleigh criterion, which states that two point-like sources are difficult toresolve if their transverse separation is smaller than the Rayleigh length.While the criterion is useful in the case of direct detection imaging, othermeasurement techniques may not be subject to this limitation. Estimatingthe angular separation between two sources is a challenging task for directimaging, especially when their angular separation is smaller than or comparableto the Rayleigh limit. In addition, if one is tasked with first discriminatingwhether there are one or two sources, then detecting the faint emission of asecondary source in the proximity of a much brighter one is in itself a severechallenge for direct imaging. Using quantum state discrimination and quantum imaging techniques, we show thatone can significantly reduce the probability of error for detecting thepresence of a weak secondary source, especially when the two sources have smallangular separations. If the weak source has intensity ε≪1 relative to the bright source, we find that theerror exponent can be improved by a factor of 1/ε. We also find linear-opticalmeasurements that are optimal in this regime [1]. We apply these techniques toLIDAR [2] as well as exoplanet detection. We then experimentally demonstrate clear sub-Rayleigh scaling for quantum statediscrimination of singular versus binary sources, and we approach the quantumCramer-Rao bound for estimating the angular separation of two sources withequal brightness. Most importantly, the two tasks can be achieved with a singlemeasurement setup: all the above tasks can be performed with a simpleinterferometer [3]. [1] Z Huang, C Lupo, Phys. Rev. Lett. 127, 130502 (2021); Editor's Selectionand Featured in Physics. [2] U Zanforlin, C Lupo, P Connolly, P Kok, G Buller, and Z Huang, accepted inNat. Comm. (2022); arXiv:2202.09406

CQT Colloquium by Lam Ping Koy, IMRE A*STAR

Title: To Be Advised
Date/Time: 20-Oct, 04:00PM
Venue: Level 3 Seminar Room (S15-03-15)

CQT Colloquium by Reinhard Werner, Leibniz University Hannover

Title: The story of quantum correlations
Date/Time: 22-Sep, 04:00PM
Venue: Level 3 Seminar Room (S15-03-15)

CQT Colloquium by Alexia Auffèves, Institut Neel - CNRS

Title:  Quantum technologies need a quantum energy initiative
Date/Time: 10-Nov, 04:00PM
Venue: Level 3 Seminar Room, S15-03-15

Abstract: Quantum technologies are currently the object of high expectations from governments and private companies, as they hold the promise to shape safer and faster ways to extract, exchange, and treat information. However, despite its major potential impact for industry and society, the question of their energetic footprint has remained in a blind spot of current deployment strategies. In this talk, I will present the motivations, ambitions and methodology for setting up a transverse quantum energy initiative (QEI), connecting quantum thermodynamics, quantum information science, quantum physics, and engineering. Such an initiative is the only path towards energy-efficient, sustainable quantum technologies, and to possibly bring out an energetic quantum advantage.

Ref: Quantum Technologies Need a Quantum Energy Initiative
Alexia Auffèves
PRX Quantum 3, 020101 – Published 1 June 2022

CQT Talk by Jun Suzuki, The University of Electro-Communications

Title:  Nagaoka-Hayashi bound in multi-parameter estimation
Date/Time: 16-Aug, 04:00PM
Venue: Level 5 Seminar Room (S15-05-14)

Abstract: We present a new bound for multi-parameter estimation for quantum states.
This bound, the Nagaoka-Hayashi bound, is tighter than any existing bound so far.
We also show that this bound can be computed efficiently as semidefinite programming.
We apply it to two examples to illustrate the importance of the finite-sample theory in quantum metrology. 

CQT Colloquium by Nicholas Bigelow, University of Rochester

Title: Experiments with Bose-Einstein Condensates aboard the Space Station: Quantum control and quantum sensing in the Coldest Spot in Space
Date/Time: 18-Aug, 04:00PM
Venue: Level 3 Seminar Room (S15-03-15)

Abstract: I will describe the work of the Consortium for Ultracold Atoms over the past four years using NASA’s and the Jet Propulsion Lab’s Cold Atom Laboratory (CAL), a shared user facility for investigating quantum matter in microgravity. In the first phases of our work we developed shortcut to adiabaticity protocols for transporting a rubidium Bose-Einstein Condensate (BEC) with positioning accuracy of ~70 nm and release velocity at or below the 100µm/s level. Deep cooling was similarly achieved using delta-kick-cooling to kinetic temperatures at or below 50 pK, creating the coldest spot in Space. I will also describe our preliminary atom interferometry experiments using both Rb and K, and our demonstration of high-performance sensing of magnetic fields and field gradients as well as preliminary tests of the Einstein Equivalence Principle.