We revisit the problem of laser-induced suppression of quantum dynamical tunneling in a model system studied by Kilin et al. [Phys. Rev. Lett. 76 (1996) 3297]. This quantum system consists of a ground state symmetric double-well potential which is coupled by a strong laser field to an excited state asymmetric double-well potential. By analyzing the assumptions used in their analysis we show that the suppression of quantum dynamical tunneling can be explained with the use of dark and bright states of the system. We also generalize the system and the conditions for suppression of quantum tunneling and show that, in certain cases, suppression can occur regardless the characteristics of the excited potential surface.
We study a model for frustrated tunneling ionization using ultrashort laser pulses. The model is based on the strong field approximation and it employs the saddle point approximation to predict quasiclassical trajectories that are captured on Rydberg states. We present a classification of the saddle-point solutions and explore their behavior as functions of angular momentum of the final state, as well as the carrier--envelope phase (CEP) of the laser pulse. We compare the final state population computed by the model to results obtained by numerical propagation of the time-dependent Schrödinger…
Using quantum computers to simulate polyatomic reaction dynamics has an exponential advantage in the amount of resources needed over classical computers. Here we demonstrate an exact simulation of the dynamics of the laser-driven isomerization reaction of asymmetric malondialdehydes. We discretize space and time, decompose the Hamiltonian operator according to the number of qubits and use Walsh-series approximation to implement the quantum circuit for diagonal operators. We observe that the reaction evolves by means of a tunneling mechanism through a potential barrier and the final state is in…
It is now common practice to solve the Schrödinger equation to estimate the tunneling current between two metal electrodes at specified potentials, or the transmission through a potential barrier by assuming an incident, reflected, and transmitted wave. However, we suggest that these methods may not be appropriate for nanoscale circuits. The electron man-free path may be as long as 68.2 nm in metallic elements so we consider the possibility that quantum effects may occur throughout a nanoscale circuit, including the connections. Analytical methods are presented for modeling the coherent transf…
We predict wide-band suppression of tunneling of spin-orbit-coupled atoms (or noninteracting Bose-Einstein condensate) in a double-well potential with periodically varying depths of the potential wells. The suppression of tunneling is possible for a single state and for superposition of two states, i.e. for a qbit. By varying spin-orbit coupling one can drastically increase the range of modulation frequencies in which an atom remains localized in one of the potential wells, the effect connected with crossing of energy levels. This range of frequencies is limited because temporal modulation may…
Purcell Enhancement and Suppression in Laser Cooling of Yb$^{3+}$:YLF Nanocrystals in a Fabry-Pérot Microcavity
Universidad de Buenos Aires, Facultad de Ciencias Exactas y Naturales（布宜诺斯艾利斯大学，理学院）；CONICET - Universidad de Buenos Aires, Instituto de Física de Buenos Aires (IFIBA)（阿根廷国家科学研究委员会-布宜诺斯艾利斯大学，布宜诺斯艾利斯物理研究所）
Ultra-low frequency noise lasers have been widely used in laser-based experiments. Most narrow-linewidth lasers are implemented by actively suppressing their frequency noise through a frequency noise servo loop (FNSL). The loop bandwidths (LBW) of FNSLs are currently below megahertz, which is gradually tricky to meet application requirements, especially for wideband quantum sensing experiments. This article has experimentally implemented an FNSL with loop-delay-limited 3.5 MHz LBW, which is an order higher than the usual FNSLs. Using this FNSL, we achieved 70 dB laser frequency noise suppressi…
Classically allowed transport is shown to compete with quantum tunneling during the ionization of atoms by ultrashort and intense laser pulses, despite Keldysh parameters smaller than unity. This is done by comparing exact probability densities with the ones obtained from purely classical propagation using the Truncated Wigner Approximation. Not only is classical transport capable of moving trajectories away from the core, but it can also furnish ionization probabilities of the same order as the quantum ones for intensities currently employed in experiments. Our results have implications rangi…
We use hollow-core fibre to preserve the spectrum and temporal profile of picosecond laser pulses in CBD to suppress 2.6 dB of amplitude noise at MHz noise frequencies, to within 0.01 dB of the shot-noise limit. We provide an enhanced version of the CBD scheme that concatenates circuits to suppress over multiple frequencies and over broad frequency ranges --- we perform a first demonstration that reduces total excess amplitude noise, between 2 - 6 MHz, by 85%. These demonstrations enable passive, broad-band, all-guided fibre laser technology operating at the shot-noise limit.
Laser intensity noise suppression has essential effects on preparation and characterization of the audio-frequency squeezed vacuum state of light based on a sub-threshold optical parametric oscillator (OPO).We have implemented two feedback loops by using relevant acousto-optical modulators (AOM) to stabilize the intensity of 795-nm near infrared (NIR) fundamental laser and 397.5-nm ultraviolet (UV) laser generated by cavity-enhanced frequency doubling.Typical peak-to-peak laser intensity fluctuation with a bandwidth of $\sim10$ kHz in a half hour has been improved from $\pm7.45$$\%$ to $\pm0.0…
Tunneling ionization of an atom in ultrashort laser pulses is considered. When the driving laser pulse is switched-on and -off with a steep slope, the photoelectron momentum distribution (PMD) shows an edge-effect because of the photoelectron diffraction by the time-slit of the pulse. The trivial diffraction pattern of the edge effect consisting of fast oscillations in the PMD disguises in the deep nonadiabatic regime the physically more interesting features in the spectrum which originate from the photoelectron dynamics. We point out the precise conditions how to avoid this scenario experimen…
Time-delay signature (TDS) suppression of semiconductor lasers with external optical feedback is necessary to ensure the security of chaos-based secure communications. Here we numerically and experimentally demonstrate a technique to effectively suppress the TDS of chaotic lasers using quantum noise. The TDS and dynamical complexity are quantified using the autocorrelation function and normalized permutation entropy at the feedback delay time, respectively. Quantum noise from quadrature fluctuations of vacuum state is prepared through balanced homodyne measurement. The effects of strength and …
We investigate the liberation of an atomic electron by a linearly polarized single-cycle near-infrared laser pulse having a peak intensity that ensures tunneling. Based on phase space analysis and energy distribution in the instantaneous potential, we reveal the importance of quantum interference between tunneling and over-the-barrier pathways of escape. Tunneling is blurred both in space and time, and the contribution of tunneling at the mean energy is almost negligible. We suggest and justify improved initial conditions for a classical particle approximation of strong-field ionization, based…
Ultrabroadband Passive Laser Noise Suppression to Quantum Noise Limit through on-chip Second Harmonic Generation
Department of Applied Physics and Ginzton laboratory, Stanford University（斯坦福大学应用物理系与金茨顿实验室）；Department of Electrical Engineering, Stanford University（斯坦福大学电气工程系）；Department of Physics, Stanford University（斯坦福大学物理系）
We report temperature-dependent current-voltage (I - V - T) and output light power-voltage or current (P - V - T) or (P - I - T) characteristics of 1550 nm tunneling injection quantum dot (TI QD) laser diodes. Experimental data is accompanied by physical models that distinguish between different current flow and light emission mechanisms for different applied voltages and temperature ranges. Three exponential regimes in the I - V characteristics were identified for low bias levels where no optical radiation takes place. At the lowest bias levels, the diffusion-recombination mechanism based on …
Nonlinear resonances in the classical phase space lead to a significant enhancement of tunneling. We demonstrate that the double resonance gives rise to a complicated tunneling peak structure. Such double resonances occur in Hamiltonian systems with an at least four-dimensional phase space. To explain the tunneling peak structure, we use the universal description of single and double resonances by 4D normal-form Hamiltonians. By applying perturbative methods, we reveal the underlying mechanism of enhancement and suppression of tunneling and obtain excellent quantitative agreement. Using a mini…
