Optimal control of uncertain quantum systems - Dahleh, M. A42 Teaching lasers to control molecules - Judson, Richard S. Warren, H. Rabitz, M. Ramakrishna, M. Salapaka, M. Dahleh, H. Rabitz, A. Controllability of molecular systems - Ramakrishna, Viswanath et al. A51 Wiseman, G.

- Lake and Sea Monsters (Mysteries, Legends, and Unexplained Phenomena).
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- An overview of Quantum Information Systems - IEEE Conference Publication.
- Innovative control system paves the way for large scale universal quantum computing.

Squeezing vi feedback. Quantum Theory of Continuous Feedback. Quantum Nondemolition Measurements - Braginsky, V. Science Issues Of Principle - Caves, C. Lloyd, R. Nelson, Y. Weinstein, D. Ernst, G. Bodenhausen, A. Oxford University Press, Oxford, Broekart, J. Jeener, J. Reson , 60 Louis-Joseph, Y. Lallemand, J. NMR 5 2 , Vathyam, S. Lee, W. Richter, S. Warren, Q. He 5 April 3 February Alicki, K. However, isolating clamped microfabricated devices from their environment is an extremely hard task.

Levitating mesoscopic objects has been suggested as a route to enable orders of magnitude improvement in thermal isolation compared to clamped devices. Experimentally, optically levitated resonators are already en par with the best clamped mechanical resonators in that respect. Levitated cavity optomechanics combines ultimate isolation from the environment with the full toolbox of cavity optomechanics available to control the quantum state of motion. The approach thus provides a route to combine the quantum state preparation techniques offered by quantum optics with the option for free-fall experiments that enable matter-wave interferometry.

I will present the state of the art in the field and results from our ongoing experiments. The latter include studies of nanoparticles in hollow-core photonic crystal fibers and cavity-optomechanical control of nanoparticles. Finally, I will discuss some of the ideas how to exploit levitated cavity optomechanics in the context of stochastic thermodynamics and for fundamental tests of quantum physics. One of the remaining issues in quantum mechanics is the apparent discrepancy between this theory and our classical world. To probe the boundary between the two realms, we propose to build a microwave interferometer that contains a travelling wave parametric amplifier TWPA in each of its arms.

Feeding the interferometer with a single photon source and studying its output radiation while varying the amplification of the TWPAs might provide more insight on the quantum-classical transition as the unitary amplifiers smoothly turn into unitarity-breaking detectors with increasing gain. In this talk we will share our results on the expected output of the interferometer and, correspondingly, how to observe a collapse of the wavefunction within the experiment.

I will present results from recent experiments where we search for multi-path interference using a far-field molecule interferometer by comparing the diffraction patterns arising from single, double and triple slits. Using a beam of phthalocyanine molecules, with a mass of amu, we have directly bounded the Sorkin-parameter using massive particles. Optomechanics in the macroscopic regime has great potential as a platform for testing fundamental principles of quantum physics, in addition to creating a new range of ultra-sensitive sensors.

In this work we demonstrate a simple and robust geometry for optical trapping in vacuum of a single nanoparticle based on a parabolic mirror and the optical gradient force. In this trap we demonstrate rapid parametric feedback cooling of all three motional degrees of freedom from room temperature to a few mK. A single laser at nm, and a single photodiode, are used for trapping, position detection, and cooling for all three dimensions. Recently, non-linear modifications of Schroedinger equation, like e.

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- The modelling of quantum control systems.

In particular, the presence of a non-linearity would explain why the wave packet associated to a quantum particle does not spread with time. In other words, particles behave as solitons, which is strongly reminiscent of de Broglie's Double Solution Program, elaborated by Louis de Broglie in the twenties, of which the de Broglie-Bohm pilot wave dynamics is a simplified version.

It is also reminiscent of Poincare's pressure, invoked by Poincare in in order to solve the wave-particle duality in the context of classical field theory. We shall describe recent attempts to derive the de Broglie-Bohm pilot wave dynamics from non-linear wave dynamics, and to apply them to quantum corpuscles at one side, and to so-called bouncing oil droplets at the other side. We can categorize this evolution with time in three different regimes.

For the intermediate time interval, quantum system decays exponentially, whereas for very short or very long time intervals, decay is not exponential. Among them a short time regime is the most interesting because, if the time interval of the observation is too short, it never decays!

One can completely halt the system from evolving. This is called as Quantum Zeno effect. The ""collapse of wave function"" playing very peculiar role here. Also, it has recently been pointed out that by exploiting the short-time features of the quantal evolution, one can also accelerate the decay. However, these effects cannot work macroscopically, because continuous or infinite measurements are physically unattainable.

But we can still use it under finite number of measurements.

Born's rule, the superposition principly, higher-order interference, and hypercomplex representations of quantum mechanics have one thing in common: They can be tested using multipath interference experiments. Going beyond the traditional double slit or interferometer we use sensitive free-space and waveguide multipath interferometers to investigate the foundations of quantum mechanics and generalized probabilistic theories. Manipulation of entanglement sudden death in an all-optical experimental set-up.

The unavoidable and irreversible interaction between an entangled quantum system and its environment causes decoherence of the individual qubits as well as degradation of the entanglement between them. En-tanglement sudden death ESD is the phenomenon wherein disentanglement happens in finite time even when individual qubits decohere only asymptotically in time due to noise. Prolonging the entanglement is essential for the practical realization of entanglement-based quantum information and computation proto-cols. For this purpose, the local NOT operation in the computational basis on one or both qubits has beenproposed.

## Transferring quantum information using sound

In this talk, I will briefly review the ESD followed by an all-optical implementation of the NOT operations such that it can hasten, delay, or completely avert ESD, all depending on when it is applied during the process of decoherence for the polarization entangled qubits as the system.

The simulation results of such manipulations [1] of ESD will be presented with the experimental progress on the same. Ashutosh Singh, Siva Pradyumna, A. A technique for non-destructive detection of trapped ions using a strongly coupled atom-cavity system will be discussed. Generalization of the technique to detect generic two-particle interactions will be suggested.

Our scheme starts with Werner-like states non-maximally entangled state mixed with white noise which satisfy Bell-CHSH inequality and introduce, in one of the parties, weak interaction involving a coupling between the particle momentum and position. The position acts like a pointer coordinate. The resulting two-party state is in general a mixed entangled state, and its entanglement is more or less than the unfiltered state, depending on what position of the pointer is post-selected.

What is particularly interesting is that in the same spirit, we can post-select states that violate the Bell-CHSH inequalities, even though the unfiltered state may not.

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Furthermore, we probe, using the filtered states, the relationship between entanglement and non-locality. This is done by comparing the concurrence versus the Bell-CHSH operator as functions of the filtered states corresponding to different values of the post-selected pointer coordinates. It is found that among this set of filtered states, the one that corresponds to maximum concurrence hence, maximum entanglement is not the one that displays maximum violation of the Bell-CHSH inequalities hence, maximum non-locality.

This demonstrates that maximum entanglement does not necessarily imply maximum non-locality. This theory provides us with a new formulation of quantum phenomena based on a unified concept of information, matter and energy.

## Quantum feedback with weak measurements - INSPIRE-HEP

We suppose that in a definite microphysicsl context, each particle is enfolded by a probability field whose existence is contingent on the existence of the particle, but it can locally affect the physical status of the particle in a context-dependent manner. The dynamics of the whole particle-field system PF system obeys deterministic equations in a manner such that when the particle is subjected to a conservative force, the form of which is determined by the dynamics of the particle.

At last we will talk about the relativistic generalization of the theory. We are going to formulate the equation of motion for PF system in a form which is Lorentz-invariant.