Coherent Control and Switching: 1st

Paul W. Brumer, Moshe Shapiro

Haruhisa Kitano, Ayami Yamaguchi, Yusaku Takahashi +5 more

The macroscopic quantum tunneling (MQT) in the current-biased intrinsic Josephson junctions (IJJs) of high- T c cuprates has attracted much attention for decades. Although the MQT for the phase switches from the zero to the first voltage state (1st SW) in the multiple-branched I-V curves is well explained by the conventional theory, the occurrence of MQT for the higher order switches such as the switch from the 1st to 2nd voltage state (2nd SW) has been still debated. Here, we present an experimental study on the phase switches of small IJJs fabricated from underdoped Bi 2 Sr 2 (Ca,Y)Cu 2 O y . We observed the single photon transition between quantized energy levels in the 3rd phase switches at 59.15 GHz and 2 K. The comparison with the previous studies on the nearly optimal-doped Bi 2 Sr 2 CaCu 2 O y clearly suggests a possibility that the MQT rate for the higher-order phase switches is commonly enhanced by the effective suppression of the energy barrier for the higher-order phase escape due to the phase-running state after the 1st SW, in spite of the large difference in a critical current density and T c .

Debabrata Goswami, Arvinder S. Sandhu

Ayami Yamaguchi, Haruka Ohnuma, Yuji Watabe +3 more

We present a study of the first and second switches (SWs) with nearly identical switching current $I_{\rm SW}$ in Bi$_2$Sr$_2$Ca$_{0.85}$Y$_{0.15}$Cu$_2$O$_y$ intrinsic Josephson junctions (IJJs). In contrast to early studies where a large difference between $I_{\rm SW}^{\rm 1st}$ and $I_{\rm SW}^{\rm 2nd}$ was observed, a crossover temperature $T_{\rm cr}$ to the quantum phase escapes for the 2nd SW is strongly reduced $(\sim$2.8~K) and agrees with that for the 1st SW. This confirms that the anomalous enhancement of $T_{\rm cr}^{\rm 2nd}$, commonly observed in the IJJs with $I_{\rm SW}^{\rm 1st} < I_{\rm SW}^{\rm 2nd}$, originates from the phase running state after the 1st SW. Detailed analysis of the microwave-induced escapes strongly suggests that nonlinear bifurcated phenomena possibly occurs in IJJs.

Sunil Sandhu, Michelle L. Povinelli, Shanhui Fan

We show that coherent control can enhance the peak pulse energy coupled into a photonic crystal (PC) resonator system. We then demonstrate two applications of this coherent control technique in a bistable PC device, namely, the reduction in input power required to switch between its bistable states and the use of phase switching to switch between its bistable states.

W. S. Warren