1,720,991 research outputs found
Electro-optic sampling of the electric-field operator for ultrabroadband pulses of Gaussian quantum light
No full textQuantum light pulses (QLPs) can be described by spatio-temporal modes, each of which is associated with a quantum state. In the mid-infrared spectral range, electro-optic sampling (EOS) provides a means to characterize quantum fluctuations in the electric field of such light pulses. Here, we present a protocol based on the two-port EOS technique that enables the complete characterization of multimode Gaussian quantum light, demonstrating robustness to both the shot noise and cascading effects. We validate this approach theoretically by reconstructing a multimode squeezed state of light generated in a thin nonlinear crystal driven by a single-cycle pulse. Our findings establish the two-port EOS technique as a versatile tool for characterizing ultrafast multimode quantum light, thereby broadening the reach of quantum state tomography. Potential applications include the characterization of complex quantum structures, such as correlations and entanglement in light and matter. Further, extensions to study multimode non-Gaussian QLPs can be envisaged.
Quasiclassical theory of non-adiabatic tunneling in nanocontacts induced by phase-controlled ultrashort light pulses
No full textWe theoretically investigate tunneling through free-space or dielectric nanogaps between metallic nanocontacts driven by ultrashort ultrabroadband light pulses. For this purpose we develop a time-dependent quasiclassical theory being especially suitable to describe the tunneling process in the non-adiabatic regime, when this process can be significantly influenced by the photon absorption as the electron moves in the classically forbidden region. Firstly, the case of driving by an ideal half-cycle pulse is studied. For different distances between the contacts, we analyze the main solutions having the form of a quasiclassical wave packet of the tunneling electron and an evanescent wave of the electron density. For each of these solutions the resulting tunneling probability is determined with the exponential accuracy inherent to the method. We identify a crossover between two tunneling regimes corresponding to both solutions in dependence on the field strength and intercontact distance that can be observed in the corresponding behaviour of the tunneling probability. Secondly, considering realistic temporal profiles of few-femtosecond pulses, we demonstrate that the preferred direction of the electron transport through the nanogap can be controlled by changing the carrier-envelope phase of the pulse, in agreement with recent experimental findings and numerical simulations. We find analytical expressions for the tunneling probability, determining the resulting charge transfer in dependence on the pulse parameters. Further, we determine temporal shifts of the outgoing electron trajectories with respect to the peaks of the laser field in dependence on the pulse phase and illustrate when the non-adiabatical character of the tunneling process is particularly important.publishe
Qubit entanglement generated by classical light driving an optical cavity
No full textWe study the generation of entanglement between two qubits which communicate through a single cavity mode of quantum light but have no direct interaction. We show that such entanglement can be generated simply by exchanging quanta with a third party, which is in our case the cavity mode. Exchanging only a single quantum creates maximal entanglement. A single quantum can be provided by an external quantum light source. However, we use a classical light source to pump quanta which are used for the exchange, and investigate the degree of two-qubit entanglement. We first identify a characteristic timescale of the interaction between the cavity mode and each qubit. We investigate two regimes of the driving pulse length: one is short and the other is long compared to the characteristic timescale of the interaction. In the first regime, it is known that the pulse can pump the system by generating a displacement of the cavity mode. We show that, by using a specific pulse shape, one can make the displacement essentially vanish after the pulse finishes interaction with the cavity mode. In this case, a rotation of the qubits can be invoked. In addition, higher-order effects of the pulse including a nonlocal operation on the joint system of the cavity mode and the qubits are found, and we present a formalism to compute each term up to a given order. An explicit condition on the pulse shape for each term to be nonzero or suppressed is derived to enable an experimental design for verifying the entanglement generation using a classical light source. In the opposite regime where the driving is sufficiently long, we utilize a squeezed state which may be obtained adiabatically. We study how the squeezing and the accompanied rotation of qubits affect the generated two-qubit entanglement.
Excitation of erbium ions in SiO2 with Si nanocrystals via virtual Auger process
No full textHere we propose a possible mechanism of fast Er3+ ions excitation in SiO2 matrix with Si nanocrystals. We show that the presence of Si nanocrystals allows for non-resonant optical pumping of erbium ions by virtual Auger transition, which is the second order process via an intermediate virtual state: the first step is the optical transition inside the Si NC, and the second one is Auger excitation of Er3+ ion accompanied by intraband transition of the confined carrier. This mechanism of excitation can take place when the energy of photon absorbed is larger than the sum of the confined electron-hole ground state energy and the excitation energy of Er3+ ion. We have calculated the excitation cross-section as a function of the excitation energy for erbium ions situated both inside and outside the NC. We show that virtually all Er3+ ions inside NCs can be excited directly into the first excited state 4I13/2 (responsible for the 1.5 μm emission) by the laser pulse of duration 5-10 ns. The results obtained for ions located outside NCs demonstrate the efficiency of the virtual excitation Auger process for transition of erbium ions into the higher excited states. 1.5 μm PL appears in this case as a result of nonradiative relaxation of excited ions down to the 4I13/2 state. Correspondingly, the rise time of the 1.5 μm PL should be about several microseconds. The cross-sections calculated demonstrate the efficiency of such Auger process.
Quantum susceptibilities in time-domain sampling of electric field fluctuations
Get PDFElectro-optic sampling has emerged as a new quantum technique enabling
measurements of electric field fluctuations on subcycle time scales. Probing a
second-order nonlinear material with an ultrashort coherent laser pulse
imprints the fluctuations of a terahertz field onto the resulting near-infrared
electrooptic signal. We describe how the statistics of this time-domain signal
can be calculated theoretically, incorporating from the onset the quantum
nature of the electric fields involved in the underlying interactions. To this
end, a microscopic quantum theory of the electro-optic process is developed
using an ensemble of non-interacting three-level systems as a model for the
nonlinear material. We find that the response of the nonlinear medium can be
separated into a classical part sampling the terahertz field and quantum
contributions independent of the state of the probed terahertz field. The
quantum response is caused by interactions between the three-level systems
mediated by the terahertz vacuum fluctuations. It arises due to cascading
processes and contributions described by quantum susceptibilities solely
accessible via quantum light. We show that the quantum contributions can be
substantial and might even dominate the total response. We also determine the
conditions under which the classical response serves as a good approximation of
the electro-optic process and demonstrate how the statistics of the sampled
terahertz field can be reconstructed from the statistics of the electro-optic
signal. In a complementary regime, electro-optic sampling can serve as a
spectroscopic tool to study the pure quantum susceptibilities of materials
Peculiarities of relief formation under InP surface sputtering will argon ions and atoms
No full textProcesses of relief formation on indium phosphide under sputtering by ion and atomic argon beam have been investigated. It is shown that depending on argon beam power density and target temperature the surface morphology formed can be either 'grass' or 'cone-in-pit' type. A quality model of surface morphology changing has been presented. The obtained results permit to explain the phenomenon of the morphology type variation.
Theory of nonradiative transitions of hot carriers in Si/SiO <sub>2</sub> nanocrystals
No full textEnergy relaxation of hot electrons and holes confined in silicon nanocrystals embedded in SiO2 matrix is studied theoretically. Phonon-assisted transitions rates strongly depend on nanocrystal diameter ranging from 108 s-1 to 10-12 s-1. The Auger-like transitions are found to be considerably faster and lead to rapid energy exchange within electron-hole pair.
Self-referenced subcycle metrology of quantum fields
No full textWe propose and analyze a new time-domain method for subcycle metrology of
quantum electric fields using a combination of a 3rd order nonlinear optical
process and homodyne detection with a local oscillator (LO) field. The new
method enables isolation of intrinsically weak quantum noise contribution by
subtraction of the shot noise of the LO on a pulse-by-pulse basis. Together
with the centro-symmetric character of the nonlinearity, our method unlocks
novel opportunities toward terahertz and mid-infrared quantum field
metrologies
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