| 1. |
- Barthelmi, K., et al.
(author)
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Atomistic defects as single-photon emitters in atomically thin MoS2
- 2020
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 117:7
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Journal article (peer-reviewed)abstract
- Precisely positioned and scalable single-photon emitters (SPEs) are highly desirable for applications in quantum technology. This Perspective discusses single-photon-emitting atomistic defects in monolayers of MoS2 that can be generated by focused He-ion irradiation with few nanometers positioning accuracy. We present the optical properties of the emitters and the possibilities to implement them into photonic and optoelectronic devices. We showcase the advantages of the presented emitters with respect to atomistic positioning, scalability, long (microsecond) lifetime, and a homogeneous emission energy within ensembles of the emitters. Moreover, we demonstrate that the emitters are stable in energy on a timescale exceeding several weeks and that temperature cycling narrows the ensembles' emission energy distribution.
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| 2. |
- Chang, J., et al.
(author)
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Detecting telecom single photons with (99.5(-2.07)(+0.5))% system detection efficiency and high time resolution
- 2021
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In: APL Photonics. - : AIP Publishing. - 2378-0967. ; 6:3
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Journal article (peer-reviewed)abstract
- Single photon detectors are indispensable tools in optics, from fundamental measurements to quantum information processing. The ability of superconducting nanowire single photon detectors (SNSPDs) to detect single photons with unprecedented efficiency, short dead time, and high time resolution over a large frequency range enabled major advances in quantum optics. However, combining near-unity system detection efficiency (SDE) with high timing performance remains an outstanding challenge. In this work, we fabricated novel SNSPDs on membranes with 99.5-(2.07)(+0.5)% SDE at 1350 nm with 32 ps timing jitter (using a room-temperature amplifier), and other detectors in the same batch showed 94%-98% SDE at 1260-1625 nm with 15-26 ps timing jitter (using cryogenic amplifiers). The SiO2/Au membrane enables broadband absorption in small SNSPDs, offering high detection efficiency in combination with high timing performance. With low-noise cryogenic amplifiers operated in the same cryostat, our efficient detectors reach a timing jitter in the range of 15-26 ps. We discuss the prime challenges in optical design, device fabrication, and accurate and reliable detection efficiency measurements to achieve high performance single photon detection. As a result, the fast developing fields of quantum information science, quantum metrology, infrared imaging, and quantum networks will greatly benefit from this far-reaching quantum detection technology.
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| 3. |
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| 4. |
- Zadeh, Iman Esmaeil, et al.
(author)
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Efficient Single-Photon Detection with 7.7 ps Time Resolution for Photon-Correlation Measurements
- 2020
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In: ACS Photonics. - : AMER CHEMICAL SOC. - 2330-4022. ; 7:7, s. 1780-1787
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Journal article (peer-reviewed)abstract
- A broad range of scientific and industrial disciplines require precise optical measurements at very low light levels. Single-photon detectors combining high efficiency and high time resolution are pivotal in such experiments. By using relatively thick films of NbTiN (8-11 nm) and improving the pattern fidelity of the nanostructure of the superconducting nanowire single-photon detectors (SNSPD), we fabricated devices demonstrating superior performance over all previously reported detectors in the combination of efficiency and time resolution. Our findings prove that small variations in the nanowire width, in the order of a few nanometers, can lead to a significant penalty on their temporal response. Addressing these issues, we consistently achieved high time resolution (best device 7.7 ps, other devices similar to 10-16 ps) simultaneously with high system detection efficiencies (80-90%) in the wavelength range of 780-1000 nm, as well as in the telecom bands (1310-1550 nm). The use of thicker films allowed us to fabricate large-area multipixel devices with homogeneous pixel performance. We first fabricated and characterized a 100 x 100 mu m(2) 16-pixel detector and showed there was little variation among individual pixels. Additionally, to showcase the power of our platform, we fabricated and characterized 4-pixel multimode fiber-coupled detectors and carried out photon-correlation experiments on a nanowire quantum dot resulting in g(2) (0) values lower than 0.04. The multipixel detectors alleviate the need for beamsplitters and can be used for higher order correlations with promising prospects not only in the field of quantum optics, but also in bioimaging applications, such as fluorescence microscopy and positron emission tomography.
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| 5. |
- Bienfang, J. C., et al.
(author)
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Materials, devices, and systems for high-speed single-photon counting
- 2022
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In: MRS bulletin. - : Springer Nature. - 0883-7694 .- 1938-1425. ; 47:5, s. 494-501
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Journal article (peer-reviewed)abstract
- Optical communications and high-speed optoelectronics are enabling technologies for modern information networks. Driven by the need for improved bandwidth, high efficiency, and low noise, advances over the last decades have led to high-performance photodetectors operating at the quantum limit. In particular, single-photon avalanche diodes (SPADs) and superconducting nanowire single-photon detectors (SNSPDs) provide excellent performance in terms of high detection efficiency and low noise. In this article, we highlight materials challenges in these detectors and review recent progress on devices, and systems for high-count-rate single-photon counting with SPADs and SNSPDs. Device configurations specifically designed for high-speed optoelectronics are discussed, including active detector readout schemes. Advantages and tradeoffs of the different device technologies are summarized and compared, providing an outlook on future prospects for performance optimization and emerging applications.
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| 6. |
- Descamps, Thomas, et al.
(author)
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Dynamic Strain Modulation of a Nanowire Quantum Dot Compatible with a Thin-Film Lithium Niobate Photonic Platform
- 2023
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In: ACS Photonics. - : American Chemical Society (ACS). - 2330-4022. ; 10:10, s. 3691-3699
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Journal article (peer-reviewed)abstract
- The integration of indistinguishable single photon sources in photonic circuits is a major prerequisite for on-chip quantum applications. Among the various high-quality sources, nanowire quantum dots can be efficiently coupled to optical waveguides because of their preferred emission direction along their growth direction. However, local tuning of the emission properties remains challenging. In this work, we transfer a nanowire quantum dot onto a bulk lithium niobate substrate and show that its emission can be dynamically tuned by acousto-optical coupling with surface acoustic waves. The purity of the single photon source is preserved during the strain modulation. We further demonstrate that the transduction is maintained even with a SiO2 encapsulation layer deposited on top of the nanowire acting as the cladding of a photonic circuit. Based on these experimental findings and numerical simulations, we introduce a device architecture consisting of a nanowire quantum dot efficiently coupled to a thin-film lithium niobate rib waveguide and strain-tunable by surface acoustic waves.
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| 7. |
- Elsinger, L., et al.
(author)
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Wavelength-resolved Purcell enhancement of PbS/CdS quantum dots measured on a chip-based platform
- 2020
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In: Proceedings of SPIE - The International Society for Optical Engineering. - : SPIE.
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Conference paper (peer-reviewed)abstract
- Future quantum optical networks will require an integrated solution to multiplex suitable sources and detectors on a low-loss platform. Here we combined superconducting single-photon detectors with colloidal PbS/CdS quantum dots (QDs) and low-loss silicon nitride passive photonic components to show their combined operation at cryogenic temperatures. Using a planar concave grating spectrometer, we performed wavelength-resolved measurements of the photoluminescence decay of QDs, which were deterministically placed in the gap of plasmonic antennas, in order to improve their emission rate. We observed a Purcell enhancement matching the antenna simulations, with a concurrent increase of the count rate on the superconducting detectors.
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| 8. |
- Esmaeil Zadeh, Iman, et al.
(author)
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Superconducting nanowire single-photon detectors : A perspective on evolution, state-of-the-art, future developments, and applications
- 2021
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In: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 118:19
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Journal article (peer-reviewed)abstract
- Two decades after their demonstration, superconducting nanowire single-photon detectors (SNSPDs) have become indispensable tools for quantum photonics as well as for many other photon-starved applications. This invention has not only led to a burgeoning academic field with a wide range of applications but also triggered industrial efforts. Current state-of-the-art SNSPDs combine near-unity detection efficiency over a wide spectral range, low dark counts, short dead times, and picosecond time resolution. The present perspective discusses important milestones and progress of SNSPDs research, emerging applications, and future challenges and gives an outlook on technological developments required to bring SNSPDs to the next level: a photon-counting, fast time-tagging imaging, and multi-pixel technology that is also compatible with quantum photonic integrated circuits.
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| 9. |
- Gao, Jun, et al.
(author)
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Scalable Generation and Detection of on-Demand W States in Nanophotonic Circuits
- 2023
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In: Nano Letters. - : American Chemical Society (ACS). - 1530-6984 .- 1530-6992. ; 23:11, s. 5350-5357
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Journal article (peer-reviewed)abstract
- Quantum physics phenomena,entanglement and coherence,are crucialfor quantum information protocols, but understanding these in systemswith more than two parts is challenging due to increasing complexity.The W state, a multipartite entangled state, is notable for its robustnessand benefits in quantum communication. Here, we generate eight-modeon-demand single-photon W states, using nanowire quantum dots anda silicon nitride photonic chip. We demonstrate a reliable and scalabletechnique for reconstructing the W state in photonic circuits usingFourier and real-space imaging, supported by the Gerchberg-Saxtonphase retrieval algorithm. Additionally, we utilize an entanglementwitness to distinguish between mixed and entangled states, therebyaffirming the entangled nature of our generated state. The study providesa new imaging approach of assessing multipartite entanglement in Wstates, paving the way for further progress in image processing andFourier-space analysis techniques for complex quantum systems.
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| 10. |
- Hanschke, Lukas, et al.
(author)
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Origin of Antibunching in Resonance Fluorescence
- 2020
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In: Physical Review Letters. - : American Physical Society. - 0031-9007 .- 1079-7114. ; 125:17
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Journal article (peer-reviewed)abstract
- Resonance fluorescence has played a major role in quantum optics with predictions and later experimental confirmation of nonclassical features of its emitted light such as antibunching or squeezing. In the Rayleigh regime where most of the light originates from the scattering of photons with subnatural linewidth, antibunching would appear to coexist with sharp spectral lines. Here, we demonstrate that this simultaneous observation of subnatural linewidth and antibunching is not possible with simple resonant excitation. Using an epitaxial quantum dot for the two-level system, we independently confirm the single-photon character and subnatural linewidth by demonstrating antibunching in a Hanbury Brown and Twiss type setup and using high-resolution spectroscopy, respectively. However, when filtering the coherently scattered photons with filter bandwidths on the order of the homogeneous linewidth of the excited state of the two-level system, the antibunching dip vanishes in the correlation measurement. Our observation is explained by antibunching originating from photon-interferences between the coherent scattering and a weak incoherent signal in a skewed squeezed state. This prefigures schemes to achieve simultaneous subnatural linewidth and antibunched emission.
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