arXiv subjects

Emanuele Distante

Publications and source records attributed to Emanuele Distante.

13 recordsLinked to original sources

arXiv2026

Metropolitan entanglement distribution between an atom and a near-visible photon

Entanglement distribution is the overarching purpose of quantum networks. While communication over long distances can use deployed fiber infrastructure, it requires photons in the telecom band. However, advanced quantum network nodes do not operate at such wavelengths. Here we overcome this limitation with two tailor-made low-noise quantum-frequency converters to distribute entanglement between a single atom and a resonant photon over 14km line-of-sight via 24km of a deployed commercial fiber. The photon at wavelength 780nm is first entangled with the atom, then converted to the telecom S-band, and finally back-converted after propagation through the fiber. This link enables a photon transfer efficiency of 1.7% while affecting the atom-photon entanglement fidelity by less than 1%. This brings integration of atomic quantum nodes with existing long-distance fiber networks into reach, enabling novel applications in quantum information processing.

quant-ph↗

arXiv2025

Collective vacuum-Rabi splitting with an atomic spin wave coupled to a cavity mode

A promising platform for quantum information research relies on cavity coupled atomic spin-waves, enabling efficient operations such as quantum memories, quantum light generation and entanglement distribution. In this work, we study the strong coupling between non-classical collective spin excitations generated by Raman scattering in a cold $^{87}\mathrm{Rb}$ atomic ensemble, and a single cavity mode. We report on an intracavity spin wave to single photon conversion efficiency of up to $\chi=0.75 \pm 0.02$ in the quantum domain, as evidenced by a violation of the Cauchy-Schwarz inequality. Our work establishes a relationship between the retrieval of an atomic spin wave in the non-classical regime and the vacuum-Rabi splitting. We show that this relationship emerges within the efficiency spectrum, and we finally provide the optimal operational conditions to achieve the maximum intrinsic retrieval efficiency. Our data is well reproduced by simulations based on optical Bloch equations. This work deepens the understanding of cavity-enhanced spin wave readout and its potential applications.

quant-ph↗

arXiv2025

Tweezer-assisted subwavelength positioning of atomic arrays in an optical cavity

We present an experimental technique that enables the preparation of defect-free arrays of 87Rb atoms within a microscopic high-finesse optical standing-wave cavity. By employing optical tweezers, we demonstrate atom positioning with a precision well below the cavity wavelength, a crucial requirement for cavity-QED experiments in which maximum atom-cavity coupling strength is required. We leverage our control capabilities to assemble an array of up to seven atoms with an efficiency that exceeds previous probabilistic methods by 4 orders of magnitude. The atoms are subsequently transferred from the tweezer array to a two-dimensional intracavity optical lattice that offers enhanced coherence for spin qubits while maintaining strong atom confinement. Our system overcomes the efficiency limitations of previous probabilistic loading techniques of cavity-coupled atom arrays and opens the path to multiqubit quantum networks with atoms strongly coupled to optical cavities.

quant-ph↗

arXiv2024

A nondestructive Bell-state measurement on two distant atomic qubits

One of the most fascinating aspects of quantum networks is their capability to distribute entanglement as a nonlocal communication resource. In a first step, this requires network-ready devices that can generate and store entangled states. Another crucial step, however, is to develop measurement techniques that allow for entanglement detection. Demonstrations for different platforms suffer from being either not complete, or destructive, or local. Here we demonstrate a complete and nondestructive measurement scheme that always projects any initial state of two spatially separated network nodes onto a maximally entangled state. Each node consists of an atom trapped inside an optical resonator from which two photons are successively reflected. Polarisation measurements on the photons discriminate between the four maximally entangled states. Remarkably, such states are not destroyed by our measurement. In the future, our technique might serve to probe the decay of entanglement and to stabilise it against dephasing via repeated measurements.

quant-ph↗

arXiv2024

A quantum-network register assembled with optical tweezers in an optical cavity

Quantum computation and quantum communication are expected to provide users with capabilities inaccessible by classical physics. However, scalability to larger systems with many qubits is challenging. One solution is to develop a quantum network consisting of small-scale quantum registers containing computation qubits that are reversibly interfaced to communication qubits. Here we report on a register that uses both optical tweezers and optical lattices to deterministically assemble a two-dimensional array of atoms in an optical cavity. Harnessing a single-atom addressing beam, we stimulate the emission of a photon from each atom and demonstrate multiplexed atom-photon entanglement with a generation-to-detection efficiency approaching 90$\%$. Combined with cavity-mediated quantum logic, our approach provides a possible route to distributed quantum information processing.

quant-ph↗

arXiv2021

Detecting an Itinerant Optical Photon Twice without Destroying It

Nondestructive quantum measurements are central for quantum physics applications ranging from quantum sensing to quantum computing and quantum communication. Employing the toolbox of cavity quantum electrodynamics, we here concatenate two identical nondestructive photon detectors to repeatedly detect and track a single photon propagating through a $60\,\mathrm{m}$ long optical fiber. By demonstrating that the combined signal-to-noise ratio of the two detectors surpasses each single one by about two orders of magnitude, we experimentally verify a key practical benefit of cascaded non-demolition detectors compared to conventional absorbing devices.

quant-ph↗

arXiv2021

Quantum Teleportation between Remote Qubit Memories with Only a Single Photon as a Resource

Quantum teleportation enables the deterministic exchange of qubits via lossy channels. While it is commonly believed that unconditional teleportation requires a preshared entangled qubit pair, here we demonstrate a protocol that is in principle unconditional and requires only a single photon as an ex-ante prepared resource. The photon successively interacts, first, with the receiver and then with the sender qubit memory. Its detection, followed by classical communication, heralds a successful teleportation. We teleport six mutually unbiased qubit states with average fidelity $\overline{\text{F}}=(88.3\pm1.3)\%$ at a rate of $6\,\mathrm{Hz}$ over $60\,\mathrm{m}$.

quant-ph↗

arXiv2021

A Quantum-Logic Gate between Distant Quantum-Network Modules

The big challenge in quantum computing is to realize scalable multi-qubit systems with cross-talk free addressability and efficient coupling of arbitrarily selected qubits. Quantum networks promise a solution by integrating smaller qubit modules to a larger computing cluster. Such a distributed architecture, however, requires the capability to execute quantum-logic gates between distant qubits. Here we experimentally realize such a gate over a distance of 60m. We employ an ancillary photon that we successively reflect from two remote qubit modules, followed by a heralding photon detection which triggers a final qubit rotation. We use the gate for remote entanglement creation of all four Bell states. Our non-local quantum-logic gate could be extended both to multiple qubits and many modules for a tailor-made multi-qubit computing register.

quant-ph↗

arXiv2020

Transient dynamics of the quantum light retrieved from Rydberg polaritons

We study the photon statistics of weak coherent pulses propagating through a cold Rydberg atomic ensemble in the regime of Rydberg electromagnetically induced transparency. We show experimentally that the value of the second-order autocorrelation function of the transmitted light strongly depends on the position within the pulse and heavily varies during the transients of the pulse. In particular, we show that the falling edge of the transmitted pulse displays much lower values than the rest of the pulse. We derive a theoretical model that quantitatively predicts our results and explains the physical behavior involved. Finally, we use this effect to generate single photons localized within a pulse from the atomic ensemble. We show that by selecting only the last part of the transmitted pulse, the single photons show an antibunching parameter as low as 0.12 and a generation efficiency per trial larger than possible with probabilistic generation schemes with atomic ensembles.

quant-ph↗

arXiv2019

Time Entanglement between a Photon and a Spin Wave in a Multimode Solid-state Quantum Memory

The generation and distribution of entanglement are key resources in quantum repeater schemes. Temporally multiplexed systems offer time-bin encoding of quantum information which provides robustness against decoherence in fibers, crucial in long distance communication. Here we demonstrate the direct generation of entanglement in time between a photon and a collective spin excitation in a rare earth ion doped ensemble. We analyze the entanglement by mapping the atomic excitation onto a photonic qubit and by using time-bin qubits analyzers implemented with another doped crystal using the atomic frequency comb technique. Our results provide a solid-state source of entangled photons with embedded quantum memory. Moreover, the quality of the entanglement is high enough to enable a violation of a Bell inequality by more than two standard deviations.

quant-ph↗

arXiv2018

Storing single photons emitted by a quantum memory on a highly excited Rydberg state

Strong interaction between two single photons is a long standing and important goal in quantum photonics. This would enable a new regime of nonlinear optics and unlock several applications in quantum information science, including photonic quantum gates and deterministic Bell-state measurements. In the context of quantum networks, it would be important to achieve interactions between single photons from independent photon pairs storable in quantum memories. So far, most experiments showing nonlinearities at the single-photon level have used weak classical input light. Here, we demonstrate the storage and retrieval of a paired single photon emitted by an ensemble quantum memory in a strongly nonlinear medium based on highly excited Rydberg atoms. We show that nonclassical correlations between the two photons persist after retrieval from the Rydberg ensemble. Our result is an important step towards deterministic photon-photon interactions, and may enable deterministic Bell-state measurements with multimode quantum memories.

quant-ph↗

arXiv2016

Storage enhanced nonlinearities in a cold atomic Rydberg ensemble

The combination of electromagnetically induced transparency (EIT) with the nonlinear interaction between Rydberg atoms provides an effective interaction between photons. In this paper, we investigate the storage of optical pulses as collective Rydberg atomic excitations in a cold atomic ensemble. By measuring the dynamics of the stored Rydberg polaritons, we experimentally demonstrate that storing a probe pulse as Rydberg polaritons strongly enhances the Rydberg mediated interaction compared to the slow propagation case. We show that the process is characterized by two time scales. At short storage times, we observe a strong enhancement of the interaction due to the reduction of the Rydberg polariton group velocity down to zero. For longer storage times, we observe a further, weaker enhancement dominated by Rydberg induced dephasing of the multiparticle components of the state. In this regime, we observe a non-linear dependence of the Rydberg polariton coherence time with the input photon number. Our results have direct consequences in Rydberg quantum optics and enable the test of new theories of strongly interacting Rydberg systems.

physics.atom-ph↗

arXiv2012

Deterministic Super Resolution with Coherent States at the Shot Noise Limit

Interference of light fields plays an important role in various high-precision measurement schemes. It has been shown that super resolving phase measurements beyond the standard coherent state limit can be obtained either by using maximally entangled multi-particle states of light or using complex detection approaches. Here we show that super resolving phase measurements at the shot noise limit can be achieved without resorting to non-classical optical states or to low-efficiency detection processes. Using robust coherent states of light, high-efficiency homodyne detection and a deterministic binarization processing technique, we show a narrowing of the interference fringes that scales with 1/Sqrt{N} where N is the mean number of photons of the coherent state. Experimentally we demonstrate a 12-fold narrowing at the shot noise limit.

quant-ph↗