All posts by cmeriles_1ry5wvws

10-19: Mishkatul Bhattacharya from the Rochester Institute of Technology tells us about how to engineer a phonon laser

Mishkatul Bhattacharya

Optical Tweezer Phonon Laser

Abstract: We are in the middle of a revolution in phononics, where it seems useful and possible to control phonons as we have photons in the last few decades. In this talk
I will describe our theoretical proposal and its experimental demonstration regarding 
a phonon laser made of the center-of-mass oscillations of a nanoparticle trapped in an
optical tweezer.  I will report on threshold behavior, coherence, subthermal number 
squeezing, time dynamics, phase space characterization, injection locking, Q switching 
and the role of stimulated emission in our single mode phonon laser. Based on this discussion 
I will conclude that our device provides a pathway for engineering a coherent source of 
phonons on the mesoscale that can be applied to both fundamental problems in quantum 
mechanics as well as tasks of precision metrology.​

08-19: Jake’s and Daniela’s paper accepted in PNAS!

Optical spin pumping of color centers promises to revolutionize the practice of nuclear magnetic resonance via efficient dynamic nuclear polarization (DNP) protocols. Significant progress has been attained with systems such as the nitrogen-vacancy (NV) center in diamond, but extreme spectral broadening and nuclear spin-lattice relaxation from co-existing paramagnetic defects are hurdles still difficult to circumvent. The technique we present in this manuscript addresses both issues through the implementation of magnetic-field-sweep-induced NV cross-relaxation with ancilla point defects, here acting as proxies to mediate the transfer of polarization to the nuclear spin ensemble. The governing spin dynamics is robust to field misalignment and ideally suited for shallow NVs, indirectly coupled to outside nuclei through paramagnetic defects at the diamond surface.

06-19: We welcome Keishlyann Báez Cruz, our IDEALS-REU student guest this summer.

Keishlyann joins us this summer from the University of Puerto Rico at Mayagüez (UPRM), where she is majoring in Chemical Engineering with a certificate in Materials Science and Engineering. Her research experience includes prior work with Al alloys, and nanoporous metals under the supervision of Prof. O. Marcelo Suarez. Last year, she also joined the Material Advantage UPRM Chapter (the only materials sciences association in the Caribbean) where she conducted a number of activities aimed at increasing the enrollment of high-school students in STEM careers. We are very happy to have you here!

03-19: Pablo’s paper on proxy-spin-mediated dynamic nuclear polarization published in Nano Letters as ASAP article.

Optically-pumped color centers in semiconductor powders can potentially induce high levels of nuclear spin polarization in surrounding solids or fluids at or near ambient conditions, but complications stemming from the random orientation of the particles and the presence of unpolarized paramagnetic defects hinder the flow of polarization beyond the defect’s host material. Here, we theoretically study the spin dynamics of interacting nitrogen-vacancy (NV) and substitutional nitrogen (P1) centers in diamond to show that outside protons spin-polarize efficiently upon a magnetic field sweep across the NV–P1 level anti-crossing. The process can be interpreted in terms of an NV–P1 spin ratchet, whose handedness —and hence the sign of the resulting nuclear polarization — depends on the relative timing of the optical excitation pulse. Further, we find that the polarization transfer mechanism is robust to NV misalignment relative to the external magnetic field, and efficient over a broad range of electron-electron and electron-nuclear spin couplings, even if proxy spins feature short coherence or spin-lattice relaxation times. Therefore, these results pave the route towards the dynamic nuclear polarization of arbitrary spin targets brought in proximity with a diamond powder under ambient conditions.