Correlations in systems with spin degree of freedom are at the heart of fundamental phenomena, ranging from magnetism to superconductivity. The e ects of correlations depend strongly on dimensionality, a striking example being one-dimensional (1D) electronic systems, extensively studied theoretically over the past fifty years 1-7 . However, the experimental investigation of the role of spin multiplicity in 1D fermions-and especially for more than two spin components-is still lacking. Here we report on the realization of 1D, strongly correlated liquids of ultracold fermions interacting repulsively within SU(N) symmetry, with a tunable number N of spin components. We observe that static and dynamic properties of the system deviate from those of ideal fermions and, for N > 2, from those of a spin-1/2 Luttinger liquid. In the large-N limit, the system exhibits properties of a bosonic spinless liquid. Our results provide a testing ground for many-body theories and may lead to the observation of fundamental 1D e ects 8 . One-dimensional quantum systems show specific, sometimes counterintuitive behaviours that are absent in the 3D world. These behaviours, predicted by many-body models of interacting bosons 9 and fermions 2-4 , include the 'fermionization' of bosons 10 and the separation of spin and density (most commonly referred to as 'charge') branches in the excitation spectrum of interacting fermions. The last phenomenon is predicted within the celebrated Luttinger liquid model 5 , which describes the low-energy excitations of interacting spin-1/2 fermions. Although the Luttinger approach describes qualitatively the physics of a number of 1D systems 11,12 , the problem of how to extend it to a more detailed description of real systems has puzzled physicists over the years 7 . In this exploration the physics of spin has played a key role.Ultracold atoms have proved to be a precious resource to study 1D physics, as they afford exceptional control over experimental parameters. Most of the experiments so far have been performed with spinless bosons, which for instance led to the realization of a Tonks-Girardeau gas 13,14 . On the other hand, 1D ultracold fermions are a promising system to observe a number of elusive phenomena, such as Stoner's itinerant ferromagnetism 15 and the physics of spin-incoherent Luttinger liquids 6 . However, only a few pioneering works, dealing with spin-1/2 particles [16][17][18] , have been reported so far.In parallel, ultracold two-electron atoms have been recently proposed for the realization of large-spin systems with SU(N ) interaction symmetry 19,20 , and the first experimental investigations have been reported 21 . This novel platform enables the simulation of 1D systems with a high degree of complexity, including spin-orbitcoupled materials 22 or SU(N ) Heisenberg and Hubbard chains 23,24 . Moreover, the investigation of these multi-component fermions is relevant for the simulation of field theories with extended SU(N ) symmetries 25 . In this Letter we report on the realization of ...
We report on the first direct observation of fast spin-exchange coherent oscillations between different long-lived electronic orbitals of ultracold 173 Yb fermions. We measure, in a model-independent way, the strength of the exchange interaction driving this coherent process. This observation allows us to retrieve important information on the interorbital collisional properties of 173 Yb atoms and paves the way to novel quantum simulations of paradigmatic models of two-orbital quantum magnetism. DOI: 10.1103/PhysRevLett.113.120402 PACS numbers: 03.75.Ss, 34.50.Cx, 37.10.Jk, 67.85.Lm Alkaline-earth-like (AEL) atoms are providing a new valuable experimental platform for advancing the possibilities of quantum simulation with ultracold gases [1]. For instance, the purely nuclear spin of ground-state AEL fermionic isotopes results in the independence of the atom-atom scattering properties from the nuclear spin projection. This feature has enabled the investigation of multicomponent 173 Yb fermions with SUðNÞ interaction symmetry both in optical lattices [2] and in onedimensional quantum wires [3]. In addition to their nuclear spin, AEL atoms offer experimental access to supplementary degrees of freedom, in particular, to a long-lived electronically excited state jei ¼ j 3 P 0 i which can be coherently populated from the ground state jgi ¼ j 1 S 0 i by optical excitation on an ultranarrow clock transition. The possibility of coherently manipulating both the orbital and the spin degree of freedom has recently been envisioned to grant the realization of paradigmatic models of two-orbital magnetism, like the Kondo model [4]. In this context, the two electronic states jgi and jei play the roles of two different orbitals.Recent experiments have investigated the SUðNÞ symmetry in jgi-jei ultracold collisions of two-electron atoms [5] and reported on first signatures of spin-exchange interactions between atoms in the two electronic states [6]. Spin-exchange interactions arise from the difference in the spin-singlet and spin-triplet potential curves in the scattering of one jgi and one jei atom. Let us assume that the two interacting atoms are in different nuclear spin states j↑i and j↓i (where the arrows are placeholders for two arbitrary nuclear spin states) and that they share the same spatial wave function. At zero magnetic field, the degeneracy of the configurations jg↑; e↓i and jg↓; e↑i, which are associated with a well-defined spin in each orbital [7], is lifted by the atom-atom interaction and the eigenstates are the orbital-symmetric (spin-singlet) jeg þ i and the orbitalantisymmetric (spin-triplet) jegFIG. 1 (color online). Two-orbital spin-exchange interaction in AEL atoms. (a) One atom in the ground state jgi and one atom in the long-lived electronic state jei periodically "exchange" their nuclear spins because of the different interaction energy in the spin-singlet jeg þ i and spin-triplet jeg − i two-particle states (note that in the graphical notation, the two-particle exchange symmetry is implicit [7]). (b...
Quantum technologies could largely benefit from the control of quantum emitters in sub-micrometric size crystals. These are naturally prone to integration in hybrid devices, including heterostructures and complex photonic devices. Currently available quantum emitters in nanocrystals suffer from spectral instability, preventing their use as single-photon sources for most quantum optics operations. In this work we report on the performances of single-photon emission from organic nanocrystals (average size of hundreds of nm), made of anthracene (Ac) and doped with dibenzoterrylene (DBT) molecules. The source has hours-long photostability with respect to frequency and intensity, both at room and at cryogenic temperature. When cooled to 3 K, the 00-zero phonon line shows linewidth values (50 MHz) close to the lifetime limit. Such optical properties in a nanocrystalline environment recommend the proposed organic nanocrystals as single-photon sources for integrated photonic quantum technologies.
Isolating single molecules in the solid state has allowed fundamental experiments in basic and applied sciences. When cooled down to liquid helium temperature, certain molecules show transition lines, that are tens of megahertz wide, limited only by the excited state lifetime. The extreme flexibility in the synthesis of organic materials provides, at low costs, a wide palette of emission wavelengths and supporting matrices for such single chromophores. In the last decades, the controlled coupling to photonic structures has led to an optimized interaction efficiency with light. Molecules can hence be operated as single photon sources and as non-linear elements with competitive performance in terms of coherence, scalability and compatibility with diverse integrated platforms. Moreover, they can be used as transducers for the optical read-out of fields and material properties, with the promise of single-quanta resolution in the sensing of charges and motion. We show that quantum emitters based on single molecules hold promise to play a key role in the development of quantum science and technologies.Modern societies have an ever-growing need for efficient computation techniques and for fast and secure communication, to distribute a huge amount of data around the globe. By harnessing quantum effects present at the nanoscale, new quantum technologies can be employed to meet these needs, including quantum cryptography and fully-fledged quantum information processing. On the other hand, the extreme sensitivity of quantum systems to their local environment can be exploited to also create new sensing devices, which provide unprecedented precision, accuracy and resolution and can be deployed within large quantum networks. Key applications require the generation and manipulation of quantum states of light, such as photonic quantum simulation [1, 2], linear optical quantum computing [3], device-independent or long-distance quantum key distribution protocols [4], sub-shot-noise imaging [5] and quantum metrology [6,7]. In this context, single impurities in solid-state systems can act as bright, on-demand single-photon sources (SPSs), which are a crucial resource in these photonic quantum technologies. Quantum emitters may also perform as non-linear elements at the few-photon level [8] and as nanoscale sensors, allowing the optical read-out of local properties of materials and fields. In this context, single molecules in the solid-state offer competitive and reliable properties, with several key advantages. First, they are very small and have well-defined transition dipole moments so that they can be used as nanoscopic sensors for a number of scalar and vector quantities such as pressure, strain, temperature, electric and magnetic fields, as well as optical fields. Second, organic molecules can be designed and synthesized for different parts of the visible spectrum and integrated in a range of organic matrices, a feature that is a severe limiting factor for color centers in diamond or lithographically produced semiconductor quan...
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