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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.
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
Title: Title to be advised
Date/Time: 18-Aug, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15
Abstract to be advised
Title: The story of quantum correlations
Date/Time: 22-Sep, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15
Abstract to be advised
Title: Title to be advised
Date/Time: 20-Oct, 04:00PM
Venue: CQT Level 3 Seminar Room, S15-03-15
Abstract to be advised