- 标题
- 摘要
- 关键词
- 实验方案
- 产品
-
Radiology, Lasers, Nanoparticles and Prosthetics || 7. Positron emission tomography
摘要： Positron emission tomography (PET) is a nuclear imaging modality used in clinics for cardiologic, neurologic, and oncologic studies. The PET method is based on the annihilation of positrons and electrons via converting their rest mass into two γ-photons flying in opposite directions. These two γ-photons are detected in a fashion similar to SPE or SPECT. Positron annihilation spectroscopy (PAS) is also used in condensed matter physics for determining the density and diffusivity of defects in solids. PAS is the opposite effect to pair production, which occurs when photons interact with nuclei at photon energies beyond 1 MeV. Pair production is important for cancer treatment with very hard x-rays, discussed in Chapter 9. However in this chapter we consider PET as an analytic tool.
关键词： nuclear imaging,PET,positron annihilation spectroscopy,γ-photons,Positron emission tomography,PAS
更新于2025-09-16 10:30:52
-
Self-error-rejecting quantum state transmission of entangled photons for faithful quantum communication without calibrated reference frames
摘要： We propose an alignment-free two-party polarization-entanglement transmission scheme for entangled photons by using only linear-optical elements, requiring neither ancillary photons nor calibrated reference frames. The scheme is robust against both the random channel noise and the instability of reference frames. Furthermore, the success probabilities for entanglement transmission are, in principle, improved to unity when active polarization controllers are used. The distinct characters of a simple structure, being easy to implement, and the high fidelity and efficiency make our protocol very useful for long-distance quantum communications and distributed quantum networks in practical applications. As an example, we give its application in a reference-frame-alignment-free quantum key distribution protocol with entanglement.
关键词： quantum communication,quantum key distribution,entanglement transmission,polarization-entangled photons,linear-optical elements
更新于2025-09-16 10:30:52
-
Quantum Cryptography in Advanced Networks || Coherence Proprieties of Entangled Bi-Modal Field and Its Application in Holography and Communication
摘要： This chapter examines the coherence properties of two modes of entangled photons and its application quantum communication and holography. It is proposed novel two-photon entangled sources which take into account the coherence and collective phenomena between the photon belonging to two different modes obtained in two-photon cooperative emission or Raman or lasing. The generation of the correlated bimodal entangled field in two-photon emission or Raman Pump, Stokes and anti-Stokes modes is proposed in the free space and cavity-induced emission. The application two-photon and Raman bimodal coherent field in communication and holography are given in accordance with the definition of amplitude and phase of such entangled states of light. At first, this method does not appear to be essentially different in comparison with the classical coherent state of information processing, but if we send this information in dispersive media, which separates the anti-Stokes and Stokes photons from coherent entanglement fields, the information is drastically destroyed, due to the quantum distribution of photons in the big number modes may be realized in the situation in which the mean value of strength of bimodal field tends to zero. The possibility of restoration of the signal after the propagation of the bimodal field through different fibers, we may restore the common square amplitude and phase.
关键词： quantum bimodal field,quantum communication,cooperative effects between blocks of photons,quantum holography
更新于2025-09-16 10:30:52
-
Carbon nanotube color centers in plasmonic nanocavities: A path to photon indistinguishability at telecom bands
摘要： Indistinguishable single photon generation at telecom wavelengths from solid-state quantum emitters remains a significant challenge to scalable quantum information processing. Here we demonstrate efficient generation of indistinguishable single photons directly in the telecom O-band from aryl-functionalized carbon nanotubes by overcoming the emitter quantum decoherence with plasmonic nanocavities. With an unprecedented single-photon spontaneous emission time down to 10 ps (from initially 0.7 ns) generated in the coupling scheme, we show a two-photon interference visibility at 4 K reaching up to 0.79, even without applying post selection. Cavity-enhanced quantum yields up to 74% and Purcell factors up to 415 are achieved with single-photon purities up to 99%. Our results establish the capability to fabricate fiber-based photonic devices for quantum information technology with coherent properties that can enable quantum logic.
关键词： Plasmonic nanocavities,indistinguishable single photons,telecommunication bands,carbon nanotubes
更新于2025-09-12 10:27:22
-
Characteristics of an organic photodetector with a conjugated donor and non-fullerene acceptor for indirect X-ray detection
摘要： In this study, an organic photodetector with a small band-gap donor, PBDB-T, and a non-fullerene acceptor, ITIC, was investigated as the active element in an indirect imaging system using a scintillator of the detector for indirect X-ray imaging. Compared with the common organic photodetector with a P3HT:PC70BM active layer, higher conversion e?ciencies can be expected, because the proposed detector is advantageous for visible-light absorption and carrier transport. The absorption peak of the PBDB-T:ITIC layer was located at 640 nm and was not well-matched with the emission properties of a CsI(Tl) scintillator. Therefore, a ZnSe(Te) scintillator with an emission peak at 620 nm was also tested. Compared with the P3HT:PC70BM detector, the ZnSe(Te)-coupled detector with the PBDB-T:ITIC = 1:1 active layer was 191% higher in collected current density (CCD) and 205% higher in sensitivity. The frequency response was measured with a 520 nm green LED. The detector with the PBDB-T:ITIC layer showed the -3 dB cut-o? frequency of 31.5 kHz, which was higher than the cut-o? frequency of the P3HT:PC70BM detector.
关键词： Materials for solid-state detectors,Photon detectors for UV, visible and IR photons (solid-state) (PIN diodes, APDs, Si-PMTs, G-APDs, CCDs, EBCCDs, EMCCDs, CMOS imagers, etc),X-ray detectors
更新于2025-09-12 10:27:22
-
Hybrid spin-superconducting quantum circuit mediated by deterministically prepared entangled photonic states
摘要： In hybrid quantum systems, a controllable coupling can be obtained by mediating the interactions with dynamically introduced photons. We propose a hybrid quantum architecture consisting of two nitrogen vacancy center ensembles coupled to a tunable flux qubit, which is contained on the transmission line of a multimode nonlinear superconducting coplanar waveguide resonator with an appended Josephson mixing device. We discuss the use of entangled propagating microwaves photons, which through our nonlinear wave-mixing procedure are made into macroscopically distinct quantum states. We use these states to steer the system and show that, with further amplification, we can create a similar photonic state, which has a more distinct reduction of its uncertainty. Furthermore, we show that all of this leads to a lengthened coherence time, a reasonable fidelity that decays to 0.94 and then later increases upward to stabilize at 0.6, as well as a strengthened entanglement.
关键词： squeezed Schr?dinger cat state,entangled microwaves photons,Schr?dinger cat state,flux qubit,nitrogen vacancy center ensembles,superconducting coplanar waveguide resonator,hybrid quantum systems
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Birefringent Cavities: Effects and Applications of a New Paradigm in CQED
摘要： The enhanced interaction of quantum states of light and matter within an optical resonator is a powerful tool for both addressing fundamental questions of nature and pursuing quantum technologies. Here, we discuss the impact of cavity birefringence – a lifting of the degeneracy of polarisation modes within the resonator – on both of these challenges. A novel model for such systems is experimentally veri?ed by the cavity emission of single photons with time-dependent polarisation states that evolve along their wavepacket [1]. This model is then used to demonstrate how a tailored birefringence allows for enhanced photon emission beyond previous limitations [2].
关键词： polarisation states,CQED,optical resonator,quantum states of light and matter,cavity birefringence,single photons,birefringent cavities
更新于2025-09-12 10:27:22
-
Polarization-dependent light-matter coupling and highly indistinguishable resonant fluorescence photons from quantum dot-micropillar cavities with elliptical cross section
摘要： We study the optical properties of coupled quantum dot-microcavity systems with an elliptical cross section. First, we develop an analytic model that describes the spectrum of the cavity modes that are split due to the reduced symmetry of the resonator. By coupling the quantum dot (QD) emission to the polarized fundamental cavity modes, we observe the vectorial nature of the Purcell enhancement, which depends on the intrinsic polarization of the quantum dot and its relative alignment with respect to the cavity axis. The variable interaction strength of the QD with the polarized cavity modes leads to the observation of strong and weak coupling. Finally, we demonstrate the capability of elliptical micropillars to emit single and highly indistinguishable photons (visibility of 87%).
关键词： elliptical cross section,Purcell enhancement,indistinguishable photons,quantum dot,micropillar cavities,strong and weak coupling
更新于2025-09-12 10:27:22
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Towards Storage of Sub-Megahertz Single Photons in Gradient Echo Memory
摘要： Quantum repeaters are foundational to establishing the long distance quantum communication channels necessary to create a global communication network. A quantum memory capable of storing optical quantum states is an integral component of the quantum repeater. A wide variety of mechanisms for implementing an optical quantum memory have been investigated, ranging from simple optical delay lines to complicated photon echo schemes. The scheme of interest here is the gradient echo memory (GEM). GEM has been demonstrated to be one of the most efficient memory schemes to date, with up to 87% recall efficiency and up to 1ms coherence time when performed in a cold atomic ensemble of 87Rb atoms. Until now, GEM has only been investigated with weak coherent pulses as no single photon source met the demanding spectral requirements of the memory protocol. In particular, it requires sub-megahertz linewidth photons at the atomic transitions of 87Rb. A compatible source has been developed utilising cavity-enhanced spontaneous parametric downconversion (SPDC) generating photons with a bandwidth of 429 ± 10 kHz. This is, to our knowledge, the narrowest single photon bandwidth from SPDC to date. Integration with this source enables single photon storage for the first time using GEM and allows for its single photon level characteristics to finally be investigated. Single-photon quantum memory opens up the prospect of using the system as a quantum optical gate. Storing multiple single photon states simultaneously in the quantum memory can potentially give rise to photon-photon interactions due to cross phase modulation.
关键词： single photon source,gradient echo memory,quantum repeaters,sub-megahertz linewidth photons,quantum memory
更新于2025-09-11 14:15:04
-
[IEEE 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Munich, Germany (2019.6.23-2019.6.27)] 2019 Conference on Lasers and Electro-Optics Europe & European Quantum Electronics Conference (CLEO/Europe-EQEC) - Quantum Storage of Frequency-Multiplexed Heralded Single Photons
摘要： Quantum memories for light are important devices in quantum information science, in particular for applications such as quantum networks and quantum repeaters [1]. It has been predicted that multimode quantum memories able to store independently multiple modes would greatly help the scaling of quantum networks by decreasing the entanglement generation time between remote quantum nodes [1]. Current research focuses mostly on time multiplexing in rare-earth doped crystals and in spatial multiplexing in atomic gases. Beyond these demonstrations, rare-earth doped crystals, thanks to their large inhomogeneous broadening, represent a unique quantum system which could also add another degree of freedom for multiplexing, the storage of multiple frequency modes [2]. In this contribution, we report on the first demonstration of quantum storage of a frequency multiplexed single photon into a laser-written waveguide integrated in a Pr3+:Y2SiO5 crystal. The great advantage of using a confined waveguide for this task is that the power required to prepare the quantum memory is strongly reduced due to the increased light-matter interaction in the waveguide. This enables simultaneous preparation of several memories at different frequencies, with a moderate laser power.
关键词： quantum repeaters,Quantum memory,single photons,quantum networks,frequency multiplexing
更新于2025-09-11 14:15:04