Ca+ Coulomb crystals, containing up to a few hundred laser-cooled ions, are used as a cold scaffold to undertake reaction studies between sympathetically cooled, rare gas ions (Xe+
, Kr+ and Ar+) and polar molecules (NH3, ND3, H2O and D2O) [1-3]. The Coulomb crystal environment allows for the accurate calculation of reaction rate coefficients under almost perturbation-free conditions, thanks...
The ALPHA (Antihydrogen Laser PHysics Apparatus) Collaboration at CERN is engaged in precise measurements of the antihydrogen spectrum with a view to studying the fundamental symmetries between matter and antimatter. In 2018, ALPHA measured the 1S-2S transition to one part in 1012 [1]. Since then, ALPHA has gone on to measure the
transitions between the 1S ground state and the 2P1/2 and...
The ALPHA (Antihydrogen Laser Physics Apparatus) collaboration has performed several precision tests of fundamental symmetries through laser and microwave spectroscopy of atomic transitions in the antihydrogen atom [1, 2, 3]. Since typically only around only twenty antihydrogen atoms are trapped per experimental cycle, in these experiments antihydrogen atoms are accumulated [4] over time...
I present a novel scheme for producing cold (magnetically trappable) atomic hydrogen, based on threshold photodissociation of the BaH+ molecular ion. BaH+ can be sympathetically cooled using laser cooled Ba+ in an ion trap, before it is photodissociated on the single photon A1Σ+←X1Σ+ transition. The small mass ratio between Ba+ and BaH+ ensures a strong overlap within the ion trap for...
A practical quantum computer, capable of solving disruptive problems, may require thousands to millions of qubits in order to execute the required quantum error correction. Scaling ion trap quantum computers to larger numbers of qubits has become a prominent area of research [1,2]. However, the number of ions that can be hosted on a single quantum computing module is limited by the size of the...
Trapped Rydberg ions [1] are a novel approach for quantum information processing. By combining the high degree of control of trapped ions with the strong dipolar interaction of Rydberg atoms, fast and motion-independent entangling gates may be realized in large ion crystals.
In our experiment, we excite trapped 88Sr+ ions to Rydberg states. We have observed strong interaction between...
Optical qubit transitions in laser-cooled, trapped ions are used in precision quantum metrology [1] and in quantum information processing [2,3]. In linear ion strings, each qubit and the quantised collective motion are controlled coherently via the ion-laser laser interaction to create scalable entanglement. Such systems could realise a gain in precision and overcome the quantum projection...
A system that can combine the complementary strengths of trapped ions and photons as carriers of quantum information is an appealing prospect. Ions provide long coherence times, high levels of quantum control and high-fidelity state readout, while photons are a natural choice for transmitting information over anything but very short distances. To interface these two platforms we use calcium...
Private communication over shared network infrastructure is of fundamental importance to the modern world. In classical cryptography, shared secrets cannot be created with unconditional security; real-world key exchange protocols rely on computational conjectures such as the hardness of prime factorisation to provide security against eavesdropping attacks. Quantum theory, however, promises...
Optical atomic clocks are our most precise tools to measure time and frequency. Their precision enables frequency comparisons between atoms in separate locations to probe the space-time variation of fundamental constants, the properties of dark matter, and for geodesy. Measurements on independent systems are limited by the standard quantum limit (SQL); measurements on entangled systems, in...
It has been more than a decade since highly charged ions (HCI) were first proposed as exciting candidates for next-generation frequency standards [1] and for precision tests of fundamental physics [2]. The technical obstacles hindering the development of a competitive clock based on a cold HCI have fallen one by one, starting with the extraction of an HCI from a hot plasma and sympathetic...
The development of quantum technologies for molecules has remained a long-standing challenge due to the complexity of molecular systems. We have recently developed a technique for the non-destructive detection of the internal quantum state of a single trapped molecular ion [1,2,3]. The method is based on the state-dependent coherent excitation of the motion of the molecular ion and subsequent...
Ions play a key role in the chemical evolution of our universe. The process of star and planet formation is tightly connected to the presence and abundance of these species. Their spectra are diagnostic tools for various astrophysical environments and their temporal evolution. However, laboratory spectra of most ions relevant to astrophysics are not available. Moreover, predicted spectra from...
In this talk, we discuss two directions of scaling up the trapped-ion system for quantum computation and quantum simulation. The first one is to use vibrational degrees of freedom in a linear chain of ions and the second one is to use internal degrees of freedom in the 2D crystals of ions.
Recently, the vibrational degrees of freedom of trapped ions have been extensively studied and are...
Precision spectroscopy with trapped ion crystals subject to correlated dephasing can reveal a multitude of information in the absence of any single-particle coherences. We present measurements of ion-ion distances, transition frequency shifts and single-shot measurements of laser-ion detunings by analyzing multi-particle correlations in one- and two-dimensional ion crystals of up to 91 ions....
Today’s quantum computers are almost exclusively built for binary information processing, inherited from classical computers. Yet, the underlying quantum systems, in particular trapped ions, are inherently multilevel systems. I will discuss how to construct a universal toolbox for quantum information processing in (almost) the full Hilbert space of Ca40 ions. We demonstrate that the...
Optomechanical systems in the quantum regime allow us to probe quantum mechanics at the boundary between the microscopic and macroscopic; these systems are also promising candidates for precision sensors. By levitating an optomechanical system in an ion trap, we decouple it from its environment, a significant advantage for quantum applications.
Interferometric methods have been used in...
This talk will summarize recent developments towards the realization of a universal integrated two-qubit quantum computation register for a register-based ion-trap quantum processor. We demonstrated high-fideltiy integrated two-qubit microwave quantum gates with infidelities approach 10-3. Through tailored pulse envelopes, we can suppress the sensitivity to the thus-far dominant source of gate...
Universal control of multiple qubits -- the ability to entangle qubits and to perform arbitrary individual qubit operations -- is a fundamental resource for quantum computing, simulation, and networking. Qubits realized in trapped atomic ions have shown the highest-fidelity two-qubit entangling operations and single-qubit rotations to date. Universal control of trapped ion qubits has...
We demonstrate coherent quantum state manipulation and precision spectroscopy of a CaH+ molecular ion based on quantum-logic spectroscopy [1-6]. Similar to atomic ions, nowadays single molecular ions can be initialized and nondestructively detected the in a pure quantum state, albeit in a probabilistic but heralded fashion [2-6]. Numerous terahertz transitions between CaH+ states with...
I will describe a quantum-enhanced sensor to detect weak motional displacements and electric fields using a large crystal of ∼ 150 trapped ions. The center-of-mass vibrational mode of the crystal serves as high-Q mechanical oscillator and the collective electronic spin as the measurement device. By entangling the oscillator and the collective spin before the motional displacement is applied...
We explore the feasibility of processing quantum information encoded in the spin of electrons trapped ion a Paul trap. The main idea is to replace the ions in a QCCD(quantum charge-coupled device) ion trap quantum computer with electrons. The combination of the low mass and simple internal structure should enable high-speed operation while allowing for high-fidelity operation. In particular,...
Laser-cooled trapped atomic ions are well-established as possessing the highest performance of any platform for quantum computing. But as importantly, the path to scaling trapped ion quantum computers involves well-defined architectural plans, from shuttling ions between quantum processor unit (QPU) cores and modular photonic interconnects between multiple QPUs to gradual error-correction...
Spectroscopy of atoms and molecules have played a central role in our understanding of physics. It has also become increasingly important to measure the fundamental physical constants such as the fine-structure constant, the Rydberg constant, the proton-electron mass ratio, or the charge radius of the proton, deuteron and the alpha particle. In order to do so, a single type of measurement is...
The use of quartz resonators for induced image current detection of trapped ions has been pioneered in a collaboration between the Universities of Granada and Mainz, aiming at developing a novel detection system for the measurement of the cyclotron frequencies of single ions. One of the anticipated applications is mass measurements of superheavy elements produced in fusion-evaporation...
In last decades room-temperature ion storage rings have proven to be unique tools for investigating properties and reaction dynamics of molecular ions, in particular the low-energy electron-ion collisions in merged beams. This is mainly due to 1) the long storage of the ions allowing relaxation of the internal ion states and 2) the ion beam target preparation for experiments at high...
The storage ring facility, DESIREE, is briefly introduced and two examples of experiments and their astrophysical implications are discussed. 1: Mutual-neutralization reactions between negative hydrogen and positive metal ions are studied in DESIREE to aid quantitative analysis of abundances of such metals from stellar spectra. 2: Polycyclic aromatic hydrocarbons (PAHs) are...
In a network of chromophores (i.e., light-absorbers) such as that in photosynthetic proteins, the chromophores interact strongly at short distances where orbital overlap is significant, and new quantum states arise after photoexcitation. These states are no longer associated with one chromophore but spatially delocalized over two or more chromophores. On the other hand, when the chromophores...
The presence of strong interactions in a many-body quantum system can lead to a variety of exotic effects. For the case of a charged impurity in a weakly interacting bosonic medium the competition of length scales can give rise to a highly correlated mesoscopic state. Its properties are vastly different from neutral quantum impurities, with a large density increase close to the ion location...
In this talk I will present measurements of chemical reactions between a single trapped Yb+ ion and an ultracold bath of Li atoms containing trace amounts of Li$_2$ dimers. This produces LiYb$^+$ molecular ions that we detect via mass spectrometry. Our results present a novel approach towards the creation of cold molecular ions and point to the exploration of ultracold chemistry in ion...
We investigate the properties of ions immersed in an atomic Bose-Einstein condensate (BEC) or an ultracold Fermi gas using variational and diagrammatic methods. For both cases, we show that the ion can form several quasiparticle states, which are charged analogues of the Fermi and Bose polarons observed in neutral atomic gases. Due to the long-range nature of the atom-ion interaction, these...
Studies of interactions between a single ion and a neutral atom, in a well-defined quantum state, constitute a corner stone in quantum chemistry. Yet, the number of techniques which enable measurement of cold collision processes and cross-section measurement is handful. We present three different fronts to improve the measurements resolution, applicability and accuracy in the measurements of...
Isolating ions and atoms from the environment is essential for experiments, especially if we aim to study quantum effects. For decades, this has been achieved by trapping ions with radiofrequency (rf) fields and neutral particles with optical fields. We are trapping ions by the interaction with light and electrostatic fields, in absence of any rf-fields. We take our results as starting point...
The talk summarizes our work on optical atomic clocks at PTB and in the quantum technology project opticlock [1] both employing trapped Yb+ ions. The 171Yb+ ion provides two atomic transitions that are well suited as a frequency reference: the S-D electric quadrupole (E2) transition at 436 nm and the S-F electric octupole (E3) transition at 467 nm. The latter is known for its yearslong excited...
In this talk, I will present incoherent and coherent frequency ratio measurements between optical atomic clocks, and the use of these measurements to constrain models of ultralight scalar dark matter. I will begin with a brief summary of the NIST Al$^+$ quantum-logic clocks, which use quantum-logic gates with a co-trapped second ion species for preparation and readout of the Al$^+$ state [1]...
The optics required for control of trapped-ion quantum systems have posed a major obstacle in scaling experimental systems, despite these qubits’ fundamental qualities. I will discuss recent work on integrated photonic approaches to trapped-ion control [1,2], which may facilitate scaling and simultaneously reduce relevant noise sources even in current small-scale experiments. In addition,...
Quantum sensors are an established technology that has created new opportunities for precision sensing across the breadth of science. Using entanglement for quantum-enhancement will allow us to construct the next generation of sensors that can approach the fundamental limits of precision allowed by quantum physics. However, determining how state-of-the-art sensing platforms may be used to...
I will present direct frequency-comb Raman spectroscopy of the $3d~^2D_{3/2}$ - $3d~^2D_{5/2}$ interval in all stable even isotopes of $^A$Ca$^+$ (A = 40, 42, 44, 46, and 48) [1,2]. With an accuracy of $\sim$20 Hz on the deduced isotope shifts, these data, combined with measurements of the $4s~^2S_{1/2}\leftrightarrow 3d~^2D_{5/2}$ transition ($\sim$2 kHz accuracy), allowed us to carry out a...
Negative molecular ions have drawn a lot of attention in recent years, because of their detection in interstellar space and of opportunities to use laser-cooled anions to cool antiproton. Cryogenic radiofrequency ion traps are well suited tools to study the quantum states and state-selected chemistry of negative ions. Using photodetachment spectroscopy we have probed rotational quantum states...
The PENTATRAP experiment located at the Max-Planck Institute for nuclear physics aims to perform mass-ratio measurements on long-lived and stable nuclides with a fractional uncertainty below 1e-11. Such high-precision mass-ratio measurements are required to assist, e.g., experiments on the determination of the neutrino mass, on the search for the fifth force and on the investigation of atomic...
The complexity and variety of molecules offer opportunities for metrology and quantum information that go beyond what is possible with atomic systems. The hydrogen molecular ion is the simplest of all molecules and can thus be calculated ab initio to very high precision [1]. Combined with spectroscopy this allows to determine fundamental constants and test fundamental theory at record...
Trapped-ion quantum technology is among the most promising candidates for the realization of a scalable quantum processor. To address individual ions and perform high-fidelity two-qubit entangling gates in a linear segmented Paul trap, we employ dynamical register reconfiguration operations to place specific qubits in a laser interaction zone. To realize fault-tolerant quantum information...
Large trapped ion crystals with N > 100 ions provide a versatile platform for quantum simulations.
Penning traps utilize static electric and magnetic fields to confine the ions and enable the
formation of large two-dimensional ion crystals with hundreds of ions. In this talk, I will discuss
recent results of electro-magnetically induced transparency (EIT) cooling that enables...
Trapped ions confined in radiofrequency traps offer an excellent degree of control, in terms of unitary operations, initialization and readout. Furthermore, advanced techniques can be employed to control external (motional) degrees of freedom. Complementing the toolbox with non-unitary operations such depolarization channels or controlled coupling to microscopic environments (ancillas) renders...
I will review two experimental developments and its applications to experiments with ion traps. First I will show how we implemented phase-stable optical forces on trapped ions, and will discuss several applications, both realized and planned. These include: spin-dependent kicking which lead to the realization of a spin heat engine, the possibility of generating giant cats, and a special kind...
We present the experimental characterization of coherence of light scattered from trapped ion crystals. We study the first and second order coherences and their dependence on the number of optical modes of employed detection setups. We show how the indistinguishable contributions from a large number of ions result in the measurement of photon bunching in a single-mode Hanbury-Brown and Twiss...
Optical atomic clocks based on cold trapped ions offer the possibilities to exploit the sophisticated tools of quantum control devoloped for quantum information processing for new protocols in frequency metrology. I will present results on optimization of such protocols towards tailored States and measurements for ion Clocks. I will also discuss prospects and challenges for quantum enhanced...
Trapped ions are known for being one of the leading quantum computing platforms as well as for their potential in metrology and sensing. Efficient interfacing of registers of trapped ions with travelling photons would allow to link them into a distributed network trapped-ion-based nodes. This can enable remarkable applications of the quantum networks e.g. in quantum enhanced distributed...
Lab tour of the atom-ion setup and the 2D crystal and tweezers labs at the University of Amsterdam. In the atom-ion lab we study molecular ion formation and in the 2D crystal lab we study quantum information with tweezers.
The virtual lab tour will show you the key components of an ion trap with all the lasers and control systems used to perform trapped Rydberg ion gate.
During this live lab tour, I will present the exiting lab of the Ion Trap group at Aarhus University!
The lab includes 3 linear Paul traps, lasers for cooling and capturing both Calcium and Barium ion, and and our ultra stable Menlo Frequency comb.
We will show our laboratory in which PTB’s Caesium beam and fountain clocks are set up and we perform research on optical atomic clocks with trapped ions.
We work on ultracold interactions and collisions of atoms, ions, and molecules using ab initio electronic structure and quanutm scattering methods.
In the virtual lab tour we will present the experimental apparatus that we have recently used to trap Ba+ ions, thus realizing the first ion trapping experiment in Italy. Moreover, we will discuss our future plans and in particular our strategy for immersing the ions into a cloud of fermionic Li atoms to observe atom-ion interactions at ultra-low temperatures.
Oxford lab, 'Two-node two-species trapped ion quantum network'
Our colleague Ludwig Krinner, is surely participating to present our lab.
