Lukáš Lachman

Bio: Lukáš Lachman is an academic researcher from Palacký University, Olomouc. The author has contributed to research in topics: Photon & Quantum. The author has an hindex of 12, co-authored 29 publications receiving 362 citations.

Pure single photons from a trapped atom source

Abstract: The work reported here has been supported by the Austrian Science Fund FWF (SINFONIA, SFB FoQuS), by the European Union (CRYTERION #227959), and by the Institut fur Quanteninformation GmbH. LS and RF acknowledge financial support from grant No. GB14-36681G of the Czech Science Foundation.

Quantum non-Gaussian Depth of Single-Photon States.

Abstract: We introduce and experimentally explore the concept of the non-Gaussian depth of single-photon states with a positive Wigner function. The depth measures the robustness of a single-photon state against optical losses. The directly witnessed quantum non-Gaussianity withstands significant attenuation, exhibiting a depth of 18 dB, while the nonclassicality remains unchanged. Quantum non-Gaussian depth is an experimentally approachable quantity that is much more robust than the negativity of the Wigner function. Furthermore, we use it to reveal significant differences between otherwise strongly nonclassical single-photon sources.

Quantum non-Gaussian multiphoton light

Abstract: We propose an experimental method of recognizing quantum non-Gaussian multiphoton states. This is a native quantum property of Fock states, the fundamental quantum states with a constant number of particles. Our method allows experimental development and characterization of higher Fock states of light, reaching even beyond the current technical limits of their generation. We experimentally demonstrate that it is capable of distinguishing realistic quantum non-Gaussian light with the mean number of photons up to five despite detection efficiency of 50%. We also provide evidence that our method can help to distinguish the number of single-photon emitters based only on their collective emission. The nonclassical nature of light sources made for quantum communication technologies can be verified even when using inefficient detectors. Quantum light has properties that cannot be duplicated using classical sources, but they are difficult to demonstrate experimentally, especially when light is lost before reaching the detector. Ivo Straka and co-workers from Palacký University in the Czech Republic have demonstrated a protocol that can prove that light containing many photons contains quantum correlations. Their experiment uses multiple photodetectors with only 50% efficiency to try and detect multiple photons simultaneously. If the light is classical the statistics of the detections must satisfy certain constraints; violation of these constraints proves the light has quantum properties. As well as witnessing the successful operation of quantum light sources, their scheme could be used to detect quantum behavior in other systems.

Hierarchy of feasible nonclassicality criteria for sources of photons

Abstract: We present an ab-initio derivation of a hierarchy of efficient nonclassicality criteria for sources of photons. The operational criteria are explicitly proposed for the linear optical multiport and feasible multiplexed single-photon detectors. The lowest criterion is equivalent to the frequently used ${g}^{(2)}(0)$ autocorrelation measurement testing the anticorrelation effect of photons. We also derive a hierarchy of criteria for the detectors capable to at least partially estimate photon-number distribution. We prove the usefulness of both hierarchies to detect the nonclassical states from the noisy multimode single-photon sources and the nonclassical states from the multiphoton sources.

Faithful Hierarchy of Genuine n-Photon Quantum Non-Gaussian Light.

Abstract: Light is an essential tool for connections between quantum devices and for diagnostic processes in quantum technology. Both applications deal with advanced nonclassical states beyond Gaussian coherent and squeezed states. Current development requires a loss-tolerant diagnostic of such nonclassical aspects. We propose and experimentally verify a faithful hierarchy of genuine n-photon quantum non-Gaussian light. We conclusively witnessed three-photon quantum non-Gaussian light in the experiment. Measured data demonstrate a direct applicability of the hierarchy for a large class of real states.

I and i

Abstract: There is, I think, something ethereal about i —the square root of minus one. I remember first hearing about it at school. It seemed an odd beast at that time—an intruder hovering on the edge of reality. Usually familiarity dulls this sense of the bizarre, but in the case of i it was the reverse: over the years the sense of its surreal nature intensified. It seemed that it was impossible to write mathematics that described the real world in …

Controlling the dynamics of spontaneous emission from quantum dots by photonic crystals

Abstract: Control of spontaneously emitted light lies at the heart of quantum optics. It is essential for diverse applications ranging from miniature lasers and light-emitting diodes, to single-photon sources for quantum information, and to solar energy harvesting. To explore such new quantum optics applications, a suitably tailored dielectric environment is required in which the vacuum fluctuations that control spontaneous emission can be manipulated. Photonic crystals provide such an environment: they strongly modify the vacuum fluctuations, causing the decay of emitted light to be accelerated or slowed down, to reveal unusual statistics, or to be completely inhibited in the ideal case of a photonic bandgap. Here we study spontaneous emission from semiconductor quantum dots embedded in inverse opal photonic crystals. We show that the spectral distribution and time-dependent decay of light emitted from excitons confined in the quantum dots are controlled by the host photonic crystal. Modified emission is observed over large frequency bandwidths of 10%, orders of magnitude larger than reported for resonant optical microcavities. Both inhibited and enhanced decay rates are observed depending on the optical emission frequency, and they are controlled by the crystals’ lattice parameter. Our experimental results provide a basis for all-solid-state dynamic control of optical quantum systems.

Microwave photonics with superconducting quantum circuits

Abstract: In the past 20 years, impressive progress has been made both experimentally and theoretically in superconducting quantum circuits, which provide a platform for manipulating microwave photons. This emerging field of superconducting quantum microwave circuits has been driven by many new interesting phenomena in microwave photonics and quantum information processing. For instance, the interaction between superconducting quantum circuits and single microwave photons can reach the regimes of strong, ultra-strong, and even deep-strong coupling. Many higher-order effects, unusual and less familiar in traditional cavity quantum electrodynamics with natural atoms, have been experimentally observed, e.g., giant Kerr effects, multi-photon processes, and single-atom induced bistability of microwave photons. These developments may lead to improved understanding of the counterintuitive properties of quantum mechanics, and speed up applications ranging from microwave photonics to superconducting quantum information processing. In this article, we review experimental and theoretical progress in microwave photonics with superconducting quantum circuits. We hope that this global review can provide a useful roadmap for this rapidly developing field.