Temperature Sensitivity of N- and N- Ground-State Manifolds.

We measure electron- and nuclear-spin transition frequencies in the ground state of nitrogen-vacancy (N-) centers in diamond for two nitrogen isotopes (N- and N-) over temperatures ranging from 77 to 400 K. Measurements are performed using Ramsey interferometry and direct optical readout of the nuclear and electron spins. We extract coupling parameters (for N-), , , , and , and their temperature dependences for both isotopes.

Dicke State Generation and Extreme Spin Squeezing via Rapid Adiabatic Passage.

Considering the unique energy level structure of the one-axis twisting Hamiltonian in combination with standard rotations, we propose the implementation of a rapid adiabatic passage scheme on the Dicke state basis. The method permits to drive Dicke states of the many-atom system into entangled states with maximum quantum Fisher information. The designed states allow us to overcome the classical limit of phase sensitivity in quantum metrology and sensing.

Two-qubit atomic gates: spatio-temporal control of Rydberg interaction.

By controlling the temporal and spatial features of light, we propose a novel protocol to prepare two-qubit entangling gates on atoms trapped at close distance, which could potentially speed up the operation of the gate from the sub-micro to the nanosecond scale. The protocol is robust to variations in the pulse areas and the position of the atoms, by virtue of the coherent properties of a dark state, which is used to drive the population through Rydberg states. From the time-domain perspective, the protocol generalizes the one proposed by Jaksch and coworkers [Jaksch , , 2000, , 2208], with three pulses that operate symmetrically in time, but with different pulse areas.

Circularly polarized light-induced potentials and the demise of excited states.

In the presence of strong electric fields, the excited states of single-electron molecules and molecules with large transient dipoles become unstable because of anti-alignment, the rotation of the molecular axis perpendicular to the field vector, where bond hardening is not possible. We show how to overcome this problem by using circularly polarized electromagnetic fields. Using a full quantum description of the electronic, vibrational, and rotational degrees of freedom, we characterize the excited electronic state dressed by the field and analyze its dependence on the bond length and angle and the stability of its vibro-rotational eigenstates.

Demonstration of diamond nuclear spin gyroscope.

We demonstrate the operation of a rotation sensor based on the nitrogen-14 (N) nuclear spins intrinsic to nitrogen-vacancy (NV) color centers in diamond. The sensor uses optical polarization and readout of the nuclei and a radio-frequency double-quantum pulse protocol that monitors N nuclear spin precession. This measurement protocol suppresses the sensitivity to temperature variations in the N quadrupole splitting, and it does not require microwave pulses resonant with the NV electron spin transitions.

Enhancement of entanglement concentration using catalysts.

Auxiliary pure quantum entangled states shared between two parties can act as catalysts in bipartite entanglement transformations. The participation of a catalyst state in the transformation can enhance its success probability. We consider transformations involving entanglement concentration of a finite number of copies of arbitrary two-qubit pure states into a single copy of a maximally entangled two-qubit pure state using bipartite local quantum operations and classical communication aided by a catalyst state.

Control defeasance by anti-alignment in the excited state.

We predict anti-alignment dynamics in the excited state of H or related homonuclear dimers in the presence of a strong field. This effect is a general indirect outcome of the strong transition dipole and large polarizabilities typically used to control or to induce alignment in the ground state. In the excited state, however, the polarizabilities have the opposite sign compared to those in the ground state, generating a torque that aligns the molecule perpendicular to the field, deeming any laser-control strategy impossible.

Anomalous Rabi Oscillations in Multilevel Quantum Systems.

We show that the excitation probability of a state within a manifold of levels undergoes Rabi oscillations with the frequency determined by the energy difference between the states and not by the pulse area, for sufficiently strong pulses. The population and coherence remains in the two-level subsystem formed by the initial and target state even at Rabi frequencies exceeding the energy difference. The observed dynamics can be useful in nonlinear spectroscopy and quantum state preparation.

Electro-magnetically controlled acoustic metamaterials with adaptive properties.

A design of actively controlled metamaterial is proposed and discussed. The metamaterial consists of layers of electrically charged nano or micro particles exposed to external magnetic field. The particles are also attached to compliant layers in a way that the designed structure exhibits two resonances: mechanical spring-mass resonance and electro-magnetic cyclotron resonance.

Vibrationally state-selective spin-orbit transfer with strong nonresonant pulses.

By dynamic Stark shift using strong nonresonant pulses, we show that it is in principle possible to prepare arbitrary superposition states of mixed multiplicity. By a proper choice of parameters, the transfer of population is shown to follow the Rabi formula, where the initial and target states are now vibrational states of two light-induced molecular potentials of different multiplicity. Starting from nonstationary wave packets, the spin transfer can proceed via parallel transfer using a single pulse or by sequential transfer using a pulse sequence.

Chirped-pulse adiabatic control in coherent anti-Stokes Raman scattering for imaging of biological structure and dynamics.

Two novel control methods based on adiabatic passage are proposed to be implemented in coherent anti-Stokes Raman scattering (CARS) microscopy for noninvasive imaging of biological structure and dynamics. The first method provides optimal pulse-area control of the resonant vibrational transitions by using a pair of equally linear-chirped pulses. The second method, named the 'roof' method, utilizes the chirp sign variation at the central time and gives robust adiabatic excitation of the resonant vibrational mode.

Optical control of the singlet-triplet transition in Rb2.

By controlling nonresonant dynamic Stark shifts it is possible to effectively decouple the intramolecular couplings of simple molecules. We have illustrated this effect in the 1 (1)Sigma(u)-->1 (3)Pi(u) transition in Rb(2). The laser scheme implies two important control knobs: the laser frequency, which must be chosen to avoid both single and multiphoton resonances and to select different electronic environments for the singlet and triplet states, and the pulse intensity, which must amplify the asymmetry in the dynamic polarizabilities that allows the decoupling, avoiding undesired strong-pulse effects.

Phase-controlled collapse and revival of entanglement of two interacting qubits.

We demonstrate the strong dependence of the entanglement dynamics of two distinguishable qubits in a trap on the relative phase of the pulses used for excitation. We show that the population and entanglement exhibits collapses and full revivals when the initial distribution of phonons is a coherent state.

Quantum phase control of entanglement.

A method of phase control of entanglement in two-qubit systems is proposed. We show that by changing a relative phase of the pulses that drive the transitions in a two-qubit system with closed-loop couplings, one can control entanglement at will. The method relies on adiabatic dynamics via time-delayed pulse sequences and can be implemented with both resonant and nonresonant transitions.

Implementing quantum gates on oriented optical isomers.

Optical enantiomers are proposed to encode molecular two-qubit information processing. Using sequences of pairs of nonresonant optimally polarized pulses, different schemes to implement quantum gates, and to prepare entangled states, are described. We discuss the role of the entanglement phase and the robustness of the pulse sequences which depend on the area theorem.

Selective excitation of vibrational states by shaping of light-induced potentials.

In this Letter we describe a method for population transfer using intense, ultrafast laser pulses. The selectivity is accomplished by careful shaping of light-induced potentials (LIPs). Creation and control of the LIPs is accomplished by choosing pairs of pulses with proper frequency detunings and time delays.