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Violations of a Leggett-Garg inequality without signaling for a photonic qutrit probed with ambiguous measurements (2018)
Journal Article
Wang, K., Emary, C., Xu, M., Zhan, X., Bian, Z., Xiao, L., & Xue, P. (2018). Violations of a Leggett-Garg inequality without signaling for a photonic qutrit probed with ambiguous measurements. Physical Review A, 97(2), doi:10.1103/PhysRevA.97.020101

We realize a quantum three-level system with photons distributed among three different spatial and polarization modes. Ambiguous measurements of the state of the qutrit are realized by blocking one out for the three modes at any one time. Using these... Read More

Enhanced violations of Leggett-Garg inequalities in an experimental three-level system (2017)
Journal Article
Wang, K., Emary, C., Zhan, X., Bian, Z., Li, J., Xue, P., & Jian, L. I. (2017). Enhanced violations of Leggett-Garg inequalities in an experimental three-level system. Optics express, 25(25), 31462-31470. doi:10.1364/OE.25.031462

Leggett-Garg inequalities are tests of macroscopic realism that can be violated by quantum mechanics. In this letter, we realise photonic Leggett-Garg tests on a three-level system and implement measurements that admit three distinct measurement outc... Read More

Ambiguous measurements, signaling, and violations of Leggett-Garg inequalities (2017)
Journal Article
Emary, C. (2017). Ambiguous measurements, signaling, and violations of Leggett-Garg inequalities. Physical Review A, 96(4), doi:10.1103/PhysRevA.96.042102

Ambiguous measurements do not reveal complete information about the system under test. Their quantum-mechanical counterparts are semiweak (or in the limit, weak) measurements and here we discuss their role in tests of the Leggett-Garg inequalities. W... Read More

Coherent control in quantum transport: Amplification, filtering and switching at finite bias (2017)
Journal Article
Thethi, R., & Emary, C. (2017). Coherent control in quantum transport: Amplification, filtering and switching at finite bias. Quantum Science and Technology, 2(2), 024011. doi:10.1088/2058-9565/aa72c8

We consider coherent feedback control of quantum transport and focus on the application of simple controllers and the effects of a finite bias voltage. We show that simple single-parameter controllers can give rise to a range of useful effects such a... Read More

Erratum to: Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality (2017)
Journal Article
Robens, C., Alt, W., Emary, C., Meschede, D., & Alberti, A. (2017). Erratum to: Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality. Applied physics. B, Lasers and optics, 123(4), 98. doi:10.1007/s00340-017-6639-5

© 2017, The Author(s). In the original version of the article, the shaded band in Fig. 3 representing the theoretical model was omitted. The original article has been revised to provide the correct figure (Fig. 3), which is also shown below. (Figure... Read More

Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality (2016)
Journal Article
Robens, C., Alt, W., Emary, C., Meschede, D., & Alberti, A. (2017). Atomic “bomb testing”: the Elitzur–Vaidman experiment violates the Leggett–Garg inequality. Applied physics. B, Lasers and optics, 123(1), doi:10.1007/s00340-016-6581-y

Elitzur and Vaidman have proposed a measurement scheme that, based on the quantum superposition principle, allows one to detect the presence of an object—in a dramatic scenario, a bomb—without interacting with it. It was pointed out by Ghirardi that... Read More

Time-of-Flight measurements of Single-Electron wave packets in quantum hall edge states (2016)
Journal Article
Kataoka, M., Johnson, N., Emary, C., See, P., Griffiths, J., Jones, G., …Jones, G. A. (2016). Time-of-Flight measurements of Single-Electron wave packets in quantum hall edge states. Physical review letters, 116(12), doi:10.1103/PhysRevLett.116.126803

We report time-of-flight measurements on electrons traveling in quantum Hall edge states. Hot-electron wave packets are emitted one per cycle into edge states formed along a depleted sample boundary. The electron arrival time is detected by driving a... Read More

Phonon emission and arrival times of electrons from a single-electron source (2016)
Journal Article
Emary, C., Dyson, A., Kataoka, M., Ryu, S., & Sim, H. (2016). Phonon emission and arrival times of electrons from a single-electron source. Physical Review B, 93(3), doi:10.1103/PhysRevB.93.035436. ISSN 2469-9950

In recent charge-pump experiments, single electrons are injected into quantum Hall edge channels at energies significantly above the Fermi level. We consider here the relaxation of these hot edge-channel electrons through longitudinal-optical-phonon... Read More

Feedback control in quantum transport (2016)
Book Chapter
Emary, C. (2016). Feedback control in quantum transport. In Understanding Complex Systems; Control of Self-Organizing Nonlinear Systems, 275-287. Springer International Publishing. doi:10.1007/978-3-319-28028-8_14

Quantum transport is the study of the motion of electrons through nano-scale structures small enough that quantum effects are important. In this contribution I review recent theoretical proposals to use the techniques of quantum feedback control to m... Read More

Maximum violations of the quantum-witness equality (2015)
Journal Article
Schild, G., & Emary, C. (2015). Maximum violations of the quantum-witness equality. Physical review. A, 92(3), (1-6). doi:10.1103/PhysRevA.92.032101. ISSN 1050-2947

We consider the quantum-witness test of macroscopic realism and derive an upper bound for possible violations of this equality due to quantum mechanics. The bound depends only on the number of possible outcomes for the blind measurement at the heart... Read More

Time-delayed feedback control of the Dicke-Hepp-Lieb superradiant quantum phase transition (2015)
Journal Article
Kopylov, W., Emary, C., Schöll, E., & Brandes, T. (2015). Time-delayed feedback control of the Dicke-Hepp-Lieb superradiant quantum phase transition. New Journal of Physics, 17(1), 013040. doi:10.1088/1367-2630/17/1/013040

We apply the time-delayed Pyragas control scheme to the dissipative Dicke model via a modulation of the atom-field-coupling. The feedback creates an infinite sequence of non-equilibrium phases with fixed points and limit cycles in the primary superra... Read More

Ideal negative measurements in quantum walks disprove theories based on classical trajectories (2015)
Journal Article
Robens, C., Alt, W., Meschede, D., Emary, C., & Alberti, A. (2015). Ideal negative measurements in quantum walks disprove theories based on classical trajectories. Physical Review X, 5(1), doi:10.1103/PhysRevX.5.011003

We report on a stringent test of the nonclassicality of the motion of a massive quantum particle, which propagates on a discrete lattice. Measuring temporal correlations of the position of single atoms performing a quantum walk, we observe a 6σ viola... Read More

Waiting time distribution for continuous stochastic systems (2014)
Journal Article
Gernert, R., Emary, C., & Klapp, S. H. (2014). Waiting time distribution for continuous stochastic systems. Physical review. E, Statistical, nonlinear, and soft matter physics, 90(6), doi:10.1103/PhysRevE.90.062115

The waiting time distribution (WTD) is a common tool for analyzing discrete stochastic processes in classical and quantum systems. However, there are many physical examples where the dynamics is continuous and only approximately discrete, or where it... Read More

Testing macroscopic realism through high-mass interferometry (2014)
Journal Article
Emary, C., Cotter, J. P., & Arndt, M. (2014). Testing macroscopic realism through high-mass interferometry. Physical review. A, 90(4), doi:10.1103/PhysRevA.90.042114

We define a quantum witness for high-mass matter-wave interferometers that allows us to test fundamental assumptions of macroscopic realism. We propose an experimental realization using absorptive laser gratings and show that such systems can strongl... Read More

Temporal quantum correlations and Leggett-Garg inequalities in multilevel systems (2014)
Journal Article
Budroni, C., & Emary, C. (2014). Temporal quantum correlations and Leggett-Garg inequalities in multilevel systems. Physical review letters, 113(5), doi:10.1103/PhysRevLett.113.050401

We show that the quantum bound for temporal correlations in a Leggett-Garg test, analogous to the Tsirelson bound for spatial correlations in a Bell test, strongly depends on the number of levels N that can be accessed by the measurement apparatus vi... Read More