Coherence Properties of Molecular Single Photons for Quantum Networks

Abstract

Quantum mechanics implies that a single photon can be in the superposition of two distant spatial modes and enable nonlocal interferences. The most vivid example is the two-photon coalescence on a 50∶50 beam splitter, known as Hong-Ou-Mandel interference. In the past decade, this experiment has been used to characterize the suitability of different single-photon sources for linear optical quantum gates. This characterization alone cannot guarantee the suitability of the photons in a scalable quantum network. As for a deeper insight, we perform a number of nonclassical interference measurements of single photons emitted by a single organic molecule that are optimized by an atomic Faraday filter. Our measurements reveal near unity visibility of the quantum interference, and a one-port correlation measurement proves the ideal Fourier limited nature of our single-photon source. A delayed choice quantum eraser allows us to observe a constructive interference between the photons, and a Hong-Ou-Mandel peak is formed additionally to the commonly observed dip. These experiments comprehensively characterize the involved photons for their use in a future quantum Internet, and they attest to the fully efficient interaction of the molecular photons with a next subsequent quantum node. They can be adapted to other emitters and will allow us to gain insights to their applicability for quantum information processing. We introduce a quality number that describes the photon's properties for their use in a quantum network; this states that effectively 97% of the utilized molecular photons can be used in a scalable quantum optical system and interact with other quantum nodes. The experiments are based on a hybridization of solid state quantum optics, atomic systems, and all-optical quantum information processing.

Polymer-encapsulated organic nanocrystals for single photon emission

“…A property of interest is the dephasing rate Γ 2 , which is the inverse of the coherence time. Many quantum information uses require all emitted photons to be indistinguishable from one another, a property which is maximised when Γ 2 is reduced to lifetime-limit of Γ 2 = Γ 1 /2 [27,29]. The measured linewidth ∆ν at a given excitation power is related to Γ 2 through [30] as shown in Fig.…”

Detuning dependent Rabi oscillations of a single molecule

“…Further experiments on triggered single photon emission are underway. These would allow to expedite a variety of quantum optical measurements with single molecules [20].…”

“…Single molecules under cryogenic conditions are known to emit highly coherent photons which are suitable for quantum interference experiments [20]. Their coherence also manifests in the recording of the photon statistics which shows coherent oscillations between the ground and excited state-so-called Rabi-oscillations [13].…”

Quantum Antennas

“…To name a few, these are plasmonic metals (such as gold, silver, aluminum, copper), [ 194 ] graphene, [ 195 ] carbon nanotubes (CNTs), [ 196–202 ] self‐assembled quantum dots (QDs) (fabricated by molecular beam epitaxy on a semiconductor substrate), [ 203 ] color defects in diamonds, [ 204–210 ] cold atoms and ions in traps, [ 211,212 ] arrays of superconducting qubits, [ 213 ] defects in 2D semiconductors, [ 214 ] and organic molecules. [ 215,216 ] With the current state of nanotechnologies, these objects can be produced/placed with nanometer precision.…”