Quantum Physics

"133Cs as a low-frequency RF field sensor Seth T. Rittenhouse,1 Seth Meiselman,2 Vanessa Ortiz,1 and Geoffrey A. Cranch2 1Department of Physics, the United States Naval Academy, Annapolis, MD 21402, USA 2Optical Sciences Division, U. S. Naval Research Laboratory, Washington, DC 20375, USA Do to the extreme sensitivity of Rydberg systems to external fields, there has been a great deal of interest in using them as high precision quantum mechanical sensors. However, for intermediate principle quantum numbers (n ∼ 20 − 40), using the AC Stark effect to measure the intensity ofan RF field is limited to amplitudes on the order of ERF ∼ 1 V/cm. In this poster we examine the feasibility of using 133Cs as a high precision, low frequency (10-100 MHz) RF field sensor. We propose using a DC field offset to increase the field sensitivity of the AC Stark spectrum to the intensity of the RF field. The presence of the DC offset field leads to sideband states with Rabbi frequencies that are highly sensitive to RF field intensity. Using electromagnetically induced transpareny, our initial theoretical modeling indicates that this approach might be used to create a RF field sensor with sub-millivolt per centimeter accuracy."

Naomy Duarte Gomes1, Barbara da Fonseca Magnani1, Jorge Douglas Massayuki Kondo2, Luis Gustavo Marcassa1 1 Instituto de Fısica de Sao Carlos, Universidade de Sao Paulo 2 Departamento de Fısica, Universidade Federal de Santa Catarina In this work, we investigate the narrowing of the electromagnetically induced transparency (EIT) profile in a three-level ladder of rubidium atoms at room temperature using a Rydberg state and a Laguerre-Gaussian mode laser. The Gaussian probe field couples the 5S1/2 → 5P3/2 states. The control field, which can be in either Gaussian or Laguerre-Gaussian (LG) modes, couples the 5P3/2 → 44D state. The EIT spectrum is measured with the polarization spectroscopy (PS) technique, resulting in a dispersive signal. The dispersive PS EIT linewidth is 20% narrower for the LG mode than for a Gaussian mode, due to the donut spatial distribution of the LG mode used. We have implemented a probe transmission model using a simplified Lindblad master equation, which allows us to calculate the PS signal and reproduces well the experimental results. The use of the PS signal eliminates the need to fit a curve when measuring EIT linewidths while still providing subnatural widths. Narrowing the transmission profile is of great interest to measure effects such as atomic collisions and mi-crowave fields. *This work is supported by grants 2016/21311-2, 2019/10971-0 and 2021/06371-7, Sao Paulo Research Foundation (FAPESP) and grant 142410/2019-5, Brazilian National Council for Scientific and Technological Development (CNPq). It is also supported by grant (W911NF2110211) from the US Army.

In cold and ultracold mixtures of atoms and molecules, Rydberg interactions with surrounding atoms or molecules may, under certain conditions, lead to the formation of special long-range Rydberg molecules [1,2,3]. These exotic molecules provide an excellent toolkit for manipulation and control of interatomic and atom-molecule interactions, with applications in ultracold chemistry, quantum information processing and many-body quantum physics. In this talk, we will discuss ultralong-range polyatomic Rydberg molecules formed when a heteronuclear diatomic molecule is bound to a Rydberg atom [3,4]. The binding mechanism appears due to anisotropic scattering of the Rydberg electron from the permanent electric dipole moment of the polar molecule. We propose an experimentally realizable scheme to produce these triatomic ultralong-range Rydberg molecules in ultracold RbCs traps, which might use the excitation of cesium or rubidium [5]. By exploiting the Rydberg electron-molecule anisotropic dipole interaction, we induce a near resonant coupling of the non-zero quantum defect Rydberg levels with the RbCs molecule in an excited rotational level. This coupling enhances the binding of the triatomic ultralong-range Rydberg molecule and produces favorable Franck-Condon factors. References [1] C. H. Greene, A. S. Dickinson, and H. R. Sadeghpour, Phys. Rev. Lett. 85, 2458 (2000). [2] S. T. Rittenhouse and H. R. Sadeghpour, Phys. Rev. Lett. 104, 243002 (2010). [3] V. Bendkowsky, B. Butscher, J. Nipper, J. P. Shaffer, R. Löw, and T. Pfau, Nature 458, 1005 (2009). [4] R. González-Férez, H. R. Sadeghpour, and P. Schmelcher, New J. Phys. 17, 013021 (2015). [5] R. González-Férez, S.T. Rittenhouse, P. Schmelcher and H.R. Sadeghpour, J. Phys. B 53, 074002 (2020)."

Junwen Zou and Stephen Hogan Resonant dipole-dipole interactions between Rydberg helium atoms and cold ground-state ammonia molecules allow Förster resonance energy transfer between the electronic degrees of freedom in the atom, and the nuclear degrees of freedom associated with the inversion of the molecule [1,2]. In this talk I will describe recent experiments in which we have exploited the Stark effect in the triplet Rydberg states in helium, with values of the principal quantum number n between 38 and 40, to tune these interactions through resonance using electric fields below 10 V/cm. Resonance widths as narrow as 70 MHz have been observed in this work. These are indicative of mean centre-of-mass collision speeds on the order of 10 m/s, and collisions that occur at temperatures significantly below 1 K. Studies of Förster resonances in this collision system are of interest in the search for dipole-bound states [3] of Rydberg atoms or molecules and polar ground-state molecules, in the exploitation of long-range dipole-dipole interactions to regulate access to ion-molecule chemistry that can occur if the polar molecule penetrates inside the Rydberg electron charge distribution [4], and for coherent control and non-destructive detection [5,6]. [1] V. Zhelyazkova and S. D. Hogan, Phys. Rev. A 95, 042710 (2017) [2] K. Gawlas and S. D. Hogan, J. Phys. Chem. Lett. 11, 83 (2020) [3] S. M. Farooqi, D. Tong, S. Krishnan, J. Stanojevic, Y. P. Zhang, J. R. Ensher, A. S. Estrin, C. Boisseau, R. Côté, E. E. Eyler and P. L. Gould, Phys. Rev. Lett. 91, 183002 (2003). [4] V. Zhelyazkova, F. B. V. Martins, J. A. Agner, H. Schmutz and F. Merkt, Phys. Rev. Lett. 125, 263401 (2020) [5] E. Kuznetsova, S. T. Rittenhouse, H. R. Sadeghpour and S. F. Yelin, Phys. Chem. Chem. Phys. 13, 17115 (2011) [6] M. Zeppenfeld, Euro. Phys. Lett. 118, 13002 (2017)

"A quantum system evolving on a manifold of discrete states can be viewed as a particle moving in a real-space lattice potential. Such a synthetic dimension provides a powerful tool for quantum simulation because of the ability to engineer many aspects of the Hamiltonian describing the system. In this talk, I will describe a synthetic dimension created from Rydberg levels in an 84-Sr atom, in which coupling between the states is induced with millimeter-waves. Tunneling amplitudes between synthetic lattice sites and on-site potentials are set by the millimeter-wave amplitudes and detunings respectively. Alternating weak and strong tunneling in a one-dimensional configuration realizes the single-particle Su-Schrieffer-Heeger Hamiltonian, a paradigmatic model of topological matter. I will also briefly describe our recent results creating ultralong-range Rydberg molecule (ULRRM) dimers in an interacting Bose gas and probing nonlocal three-body spatial correlations with ULRRM trimers. Kanungo, S.K., Whalen, J.D., Lu, Y. et al. Realizing topological edge states with Rydberg-atom synthetic dimensions. Nat Commun 13, 972 (2022). https://doi.org/10.1038/s41467-022-28550-y "

Simulation of quantum magnetism with AMO systems is now a fully fledged enterprise. In this talk, I will discuss how Rydberg molecular interactions can be exploited to simulate indirect spin-spin coupling, with Rydberg atoms acting as localized impurities. Engineering chiral spin Hamiltonians with Rydberg atoms is also described.

"We present our recent studies on Rydberg atom-Ion interactions and the spatial imaging of a novel type of molecular ion using a high-resolution ion microscope. The ion microscope provides an exceptional spatial and temporal resolution on a single atom level, where a highly tuneable magnification ranging from 200 to over 1500, a resolution better than 200nm and a depth of field of more than 70µm were demonstrated [1]. A pulsed operation mode of the microscope combined with the excellent electric field compensation enables the study of highly excited Rydberg atoms and ion-Rydberg atom hybrid systems. Using the ion microscope, we observed a novel molecular ion, where the bonding mechanism is based on the interaction between the ionic charge and an induced flipping dipole of a Rydberg atom [2]. Furthermore, we could measure the vibrational spectrum and spatially resolve the bond length and the angular alignment of the molecule. The excellent time resolution of the microscope enables probing of the interaction dynamics between the Rydberg atom and the ion. [1] C. Veit, N. Zuber, O. A. Herrera-Sancho, V. S. V. Anasuri, T. Schmid, F. Meinert, R. Löw, and T. Pfau, Pulsed Ion Microscope to Probe Quantum Gases, Phys. Rev. X 11, 011036 (2021). [2] N. Zuber, V. S. V. Anasuri, M. Berngruber, Y.-Q. Zou, F. Meinert, R. Löw, T. Pfau, Spatial imaging of a novel type of molecular ions, Nature 5, 453 (2022)"

I will discuss a recent result on an intimate link between two a priori distinct phenomena: quantum nonlocality without entanglement and classically-achievable indefinite causal order. The first phenomenon refers to a multipartite scenario where the parties are unable to perfectly discriminate orthogonal product states drawn from an ensemble of quantum states by using local operations and classical communication (LOCC). The second (hypothetical) phenomenon refers to a multipartite scenario where the parties can communicate classically but the local operations of each party are in the future of the other parties, i.e., they cannot be ordered causally. Specifically, I will show how three separated parties with access to a classical process exhibiting indefinite causal order---the AF/BW process---can perfectly discriminate the states in an ensemble---the SHIFT ensemble---that exhibits quantum nonlocality without entanglement. Time permitting, I will discuss the generalization of this result beyond the tripartite case and comment on its connection with separable operations that are outside LOCC. 

 

Based on joint work with Ämin Baumeler, arXiv:2202.00440.

Zoom Link: https://pitp.zoom.us/j/93727212623?pwd=cjVRL3cvMmhicDRic3lXRFBkNi9xZz09

 It is unknown how the Einstein Equivalence Principle (EEP) should be modified to account for quantum features. A possibility introduced in arXiv:2012.13754 is that the EEP holds in a generalized form for particles having an arbitrary quantum state. The core of this proposal is the ability to transform to a Quantum Reference Frame (QRF) associated to an arbitrary quantum state of a physical system, in which the metric is locally inertial. I will show that this extended EEP, initially formulated in terms of the local expression of the metric field in a QRF, can be verified in an interferometric setup via tests on the proper time of entangled clocks (arXiv:2112.03303). Moreover, the same setup can be analyzed with quantum sensing techniques (arXiv:2204.03006): I will talk about how gravitational time dilation may be used as a resource in quantum information theory, showing that it may enhance the precision in estimating the gravitational acceleration for long interferometric times.

 

The current theories of quantum physics and general relativity on their own do not allow us to study situations in which spacetime is in a quantum superposition. In this talk, I propose a general strategy to determine the dynamics of objects on an indefinite spacetime metric, using an extended notion of quantum reference frame transformations. First, we study the situation of the gravitational source mass being in a spatial superposition state and, using a generalized principle of covariance, show how to transform to a frame in which the standard theories of GR and QFT allow to determine the dynamics. In the second part, we consider superpositions of conformally equivalent metrics inhabited by a massive quantized Klein-Gordon field. By requiring invariance of the KG equation under quantum conformal transformations, we find that the superposition is transferred to the quantum field in the form of an effective, spacetime dependent mass term. Overall, the proposed strategy allows to construct the respective explicit quantum frame change operators, and to study physical phenomena such as time dilation and cosmological particle production in different quantum frames.

Zoom Link: https://pitp.zoom.us/j/96903859307?pwd=aEtLUy9tME5GL25nTjBVNXVmb2N3Zz09