Experimental Determination of the Quantum-Mechanical State of a Molecular Vibrational Mode Using Fluorescence Tomography

Dunn, Thomas J.; Mukamel, Shaul

doi:10.1103/physrevlett.74.884

Cited by 320 publications

(227 citation statements)

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“…Repeating this process many times and obtaining the marginals for a large number of mechanical phase-space angles θ is sufficient to uniquely determine the mechanical quantum state of motion [35]. Quantum state tomography by measurement of the marginals was first realized with optical fields using homodyne interferometry [36] and has now become an indispensable tool in the field of quantum optics [37] being applied to other physical systems such as molecular vibration [38], spin ensembles [39], and microwave fields [40]. Here we implement such mechanical state tomography by utilizing the pulsed measurement outcome probability distribution…”

Section: Experimental Protocolmentioning

confidence: 99%

Cooling-by-measurement and mechanical state tomography via pulsed optomechanics

et al. 2013

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Observing a physical quantity without disturbing it is a key capability for the control of individual quantum systems. Such back-action-evading or quantum-non-demolition measurements were first introduced in the 1970s in the context of gravitational wave detection to measure weak forces on test masses by high precision monitoring of their motion. Now, such techniques have become an indispensable tool in quantum science for preparing, manipulating, and detecting quantum states of light, atoms, and other quantum systems. Here we experimentally perform rapid optical quantumnoise-limited measurements of the position of a mechanical oscillator by using pulses of light with a duration much shorter than a period of mechanical motion. Using this back-action evading interaction we performed both state preparation and full state tomography of the mechanical motional state. We have reconstructed mechanical states with a position uncertainty reduced to 19 pm, limited by the quantum fluctuations of the optical pulse, and we have performed 'cooling-by-measurement' to reduce the mechanical mode temperature from an initial 1100 K to 16 K. Future improvements to this technique may allow for quantum squeezing of mechanical motion, even from room temperature, and reconstruction of non-classical states exhibiting negative regions in their phase-space quasi-probability distribution.Experiments are now beginning to investigate nonclassical motion of massive mechanical devices [1][2][3]. This opens up new perspectives for quantum-physics enhanced applications and for tests of the foundations of physics. A versatile approach to manipulate mechanical states of motion is provided by the interaction with electromagnetic radiation, typically confined to microwave or optical cavities. Such cavity-optomechanics experiments [4][5][6][7][8] have thus far largely concentrated on high sensitivity continuous monitoring of the mechanical position [9][10][11][12][13][14]. Because of the back-action imparted by the probe onto the measured object, the precision of such a measurement is fundamentally constrained by the standard quantum limit (SQL) [15,16], and therefore only allows for classical phase-space reconstruction [9,17,18]. In order to observe quantum mechanical features that are smaller than the mechanical zero-point motion, backaction-evading measurement techniques that can surpass the SQL [19,20] are required. Following the early insights of Braginsky, beating the standard quantum limit 'can be achieved only in one way: design the probe so it "sees" only the measured observable ' [15]. Such backaction evading techniques were first realized for the detection of optical quadratures [21][22][23] and have since been used for, e.g. precision measurement of atomic ensemble spin [24][25][26][27][28] and quantum non-demolition microwave photon counting [29]. In optomechanics, to perform a back-action evading measurement of the mechanical position, a time-dependent measurement scheme is required. One prominent example is the so-called 'two-tone app...

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Section: Experimental Protocolmentioning

confidence: 99%

Cooling-by-measurement and mechanical state tomography via pulsed optomechanics

et al. 2013

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“…This information, together with the one arising from a subsequent strong measurement, is enough to completely specify the state of the system. That is, the system quantum state can be determined from a single experiment just by measuring the probability density and its transversal flow (accounted for by the current density), unlike other traditional methods, such as quantum state tomography [6][7][8][9], which require several complementary experiments in order to obtain a full picture of the corresponding quantum state. Rigorously speaking, if |φ i and |φ f denote pre-and post-selected states of the system, respectively, the weak value rendered by a weak measurement associated with an operatorÂ is defined as…”

Section: Introductionmentioning

confidence: 99%

What dynamics can be expected for mixed states in two-slit experiments?

Luis

Sanz

2015

Annals of Physics

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Weak-measurement-based experiments [Kocsis et al., Science 332 (2011) 1170 have shown that, at least for pure states, the average evolution of independent photons in Young's two-slit experiment is in compliance with the trajectories prescribed by the Bohmian formulation of quantum mechanics. But, what happens if the same experiment is repeated assuming that the wave function associated with each particle is different, i.e., in the case of mixed (incoherent) states? This question is investigated here by means of two alternative numerical simulations of Young's experiment, purposely devised to be easily implemented and tested in the laboratory. Contrary to what could be expected a priori, it is found that even for conditions of maximal mixedness or incoherence (total lack of interference fringes), experimental data will render a puzzling and challenging outcome: the average particle trajectories will still display features analogous to those for pure states, i.e., independently of how mixedness arises, the associated dynamics is influenced by both slits at the same time. Physically this simply means that weak measurements are not able to discriminate how mixedness arises in the experiment, since they only provide information about the averaged system dynamics.

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“…Since the first theoretical proposals [1] and the pioneering experiments [2], this discipline has witnessed significant growth [3]. Laboratory demonstrations of state tomography are numerous and span a broad range of physical systems, including molecules [4], ions [5], atoms [6], spins [7], and entangled photon pairs [8].…”

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confidence: 99%