Akito Kusaka

Akito Kusaka is a Dicke fellow in the Physics department. He works with the groups of Professor Suzanne Staggs and Professor Lyman Page on the measurement of cosmic microwave background (CMB) polarization. Akito's specialization ranges from instrumentation development to data analysis. He received his PhD from the University of Tokyo in particle physics, on the measurement of the CP violation in B meson system at Belle experiment.

His research focus has been on the exploration of fundamental physics at high energies, first in colliders, and now in the early universe. Akito finds high-energy physics compelling for two reasons. First, the high-energy scale is the regime of physics that is always new to us, often allowing us to discover the fundamental structure of physics at lower energies. The second reason is the Big Bang, which tells us that the early universe was extremely hot, and that as a result, we need to understand high-energy physics to answer the ultimate question of how the universe began. In turn, observations of the initial universe have the potential to probe physics at the energy scale of 10^16GeV, which we would not otherwise have access to.

Primordial gravitational waves are a unique channel through which we can "see" the early universe, and CMB polarization is the ultimate probe of primordial gravitational waves, via the B-mode (or oddparity) signature. Inflationary models predict gravitational waves that manifest as the B-mode CMB fluctuations on degree angular scales. A detection of such a signal would be strong evidence of the inflation scenario and constitute the first observational connection between quantum physics and gravity; this would significantly impact our very basic understanding of fundamental physics.

At Princeton, Akito works for the ABS experiment, which aims to more precisely measure CMB polarization. ABS has deployed 240 polarimeters employing transition-edge sensor (TES) bolometers observing at 150 GHz. ABS will achieve one of the most precise determinations of the B-mode with its unique advantages: a continuously rotating half wave plate providing fast and clean modulation and systematically clean optics consisting of a cryogenic side-fed Dragone telescope and feedhorn coupled TES detectors.

Outside of ABS, Akito also explores new ideas on how to measure CMB polarization. He is developing new and unique concepts on instrumentation using highly multi-moded polarization sensitive sensors. This method has a potential of providing competitive sensitivity with lower cost, while also offering a wide range of frequency bands for foreground removal and good control of instrumental systematics. These are unique features that none of the other existing experiments has.

Akito is also completing results from the QUIET experiment, where he has been a leading member for more than five years. QUIET is an experiment for CMB polarization, employing a unique HEMT technology, and released results from its 40GHz and 90GHz receivers in 2011 and 2012, respectively.

Selected publications:

  • QUIET Collaboration, "The QUIET instrument," arXiv:1207.5562 (2012), submitted to Astrophys.J.
  • QUIET Collaboration, "Second Season QUIET Observations: Measurements of the CMB Polarization Power Spectrum at 95 GHz," Astrophys.J.760:145 (2012).
  • A. Kusaka et al, "MuSE: a novel experiment for CMB polarization measurement using highly multimoded bolometers," SPIE Conference Series, 8452, 84521L (2012).
  • QUIET Collaboration, "First Season QUIET Observations: Measurements of CMB Polarization Power Spectra at 43 GHz in the Multipole Range 25 <= ell <= 475," Astrophys.J.741:111 (2011).
  • Belle Collaboration, A.Kusaka, C.C.Wang et al, "Measurement of CP Asymmetries and Branching Fractions in a Time-Dependent Dalitz Analysis of B0-->(rho pi)0 and a Constraint on the Quark Mixing Angle phi2," Physical Review D, APS, Vol 77, 072001 (2008).
  • Belle Collaboration, A.Kusaka, C.C.Wang, H.Ishino et al, "Measurement of CP Asymmetry in a Time-Dependent Dalitz Analysis of B0-->(rho pi)0 and a Constraint on the Quark Mixing Angle phi2," Physical Review Letters, APS, Vol. 98, 221602 (2007).