10 likes | 169 Views
Up the photon staircase: photons repel each other Nai Phuan Ong , Princeton University, DMR 0819860 Princeton Center for Complex Materials (PCCM).
E N D
Up the photon staircase: photons repel each other NaiPhuanOng, Princeton University, DMR 0819860Princeton Center for Complex Materials (PCCM) Electrons strongly repel each other via the Coulomb force. In a quantum dot, this repulsion can be so strong that it can force the current to flow one electron at a time -- a phenomenon referred to as "coulomb blockade“ (Fig. 1). Photons are neutral, so they do not feel the Coulomb force. However, under special conditions, photons can manifest strong mutual repulsion effects. PCCM scientists Tureci and Houck have demonstrated this "photon blockade" in a device based on a superconducting “qubit” housed in a microwave resonator. When a photon occupies the resonator, it alters the resonance frequency sufficiently that a second photon is "blocked" from entering. The resulting power transmission through the resonator displays a staircase profile as a function of the incoming microwave bandwidth that is a direct experimental proof of photon blockade (Fig. 2). Just as transport experiments through quantum dots provided key insight into physics of electron transport and correlation effects in complex materials, photonic quantum dots are expected to form the building blocks of larger quantum circuits to simulate non-equilibrium quantum physics. Fig. 1 Comparison of Coulomb blockade involving electrons in a quantum dot (left) and photon blockade in cavity-qubit device (right). Transmission is step-like in both cases. 1. AJ Hoffman, SJ Srinivasan, S. Schmidt, L. Spietz, J. Aumentado, HE Tureci, AA Houck, Phys. Rev. Lett. 107, 053602 (2011). 2. AA Houck, HE Türeci and J Koch, Nat. Phys., 2 APRIL 2012 | DOI: 10.1038/NPHYS2251 Fig. 2 Theoretical simulation of the photon staircase (left) compared with the measured transmitted power through the cavity qubit device versus incident microwave bandwidth (right).