Ion Trap System Research Articles

Scalable Experimental Bounds for Entangled Quantum State Fidelities

Estimating the state preparation fidelity of highly entangled states on noisy intermediate-scale quantum (NISQ) devices is important for benchmarking and application considerations. Unfortunately, exact fidelity measurements quickly become prohibitively expensive, as they scale exponentially as O (3 N ) for N -qubit states, using full state tomography with measurements in all Pauli bases combinations. However, Somma et al. established that the complexity could be drastically reduced when looking at fidelity lower bounds for states that exhibit symmetries, such as Dicke States and GHZ States. These bounds must still be tight enough for larger states to provide reasonable estimations on NISQ devices. For the first time and more than 15 years after the theoretical introduction, we report meaningful lower bounds for the state preparation fidelity of all Dicke States up to N = 10 and all GHZ states up to N = 20 on Quantinuum H1 ion-trap systems using efficient implementations of recently proposed scalable circuits for these states. Our achieved lower bounds match or exceed previously reported exact fidelities on superconducting systems for much smaller states. Furthermore, we provide evidence that for large Dicke States \(\vert {{D_{N}^{N}{/2}}\rangle } \) , we may resort to a GHZ-based approximate state preparation to achieve better fidelity. This work provides a path forward to benchmarking entanglement as NISQ devices improve in size and quality.

Quantum Nuclear Dynamics on a Distributed Set of Ion-Trap Quantum Computing Systems.

Quantum nuclear dynamics with wavepacket time evolution is classically intractable and viewed as a promising avenue for quantum information processing. Here, we use IonQ, Inc.'s 11-qubit trapped-ion quantum computer, Harmony, to study the quantum wavepacket dynamics of a shared-proton within a short-strong hydrogen-bonded system. We also provide the first application of distributed quantum computing for chemical dynamics problems, where a distributed set of quantum processes is constructed using a tensor network formalism. For a range of initial states, we experimentally drive the ion-trap system to emulate the quantum nuclear wavepacket as it evolves along the potential surface generated from the electronic structure. Following the experimental creation of the nuclear wavepacket, we extract measurement observables such as its time-dependent spatial projection and its characteristic vibrational frequencies to good agreement with classical results. Vibrational eigenenergies obtained from quantum computation are in agreement with those obtained from classical simulations to within a fraction of a kilocalorie per mole, thus suggesting chemical accuracy. Our approach opens a new paradigm for studying the quantum chemical dynamics and vibrational spectra of molecules and also provides the first demonstration of parallel quantum computation on a distributed set of ion-trap quantum computers.

Ion trap with in-vacuum high numerical aperture imaging for a dual-species modular quantum computer.

Photonic interconnects between quantum systems will play a central role in both scalable quantum computing and quantum networking. Entanglement of remote qubits via photons has been demonstrated in many platforms; however, improving the rate of entanglement generation will be instrumental for integrating photonic links into modular quantum computers. We present an ion trap system that has the highest reported free-space photon collection efficiency for quantum networking. We use a pair of in-vacuum aspheric lenses, each with a numerical aperture of 0.8, to couple 10(1)% of the 493nm photons emitted from a 138Ba+ ion into single-mode fibers. We also demonstrate that proximal effects of the lenses on the ion position and motion can be mitigated.

Quantum entanglement of ions for light dark matter detection

A detection scheme is explored for light dark matter, such as axion dark matter or dark photon dark matter, using a Paul ion trap system. We first demonstrate that a qubit, constructed from the ground and first excited states of vibrational modes of ions in a Paul trap, can serve as an effective sensor for weak electric fields due to its resonant excitation. As a consequence, a Paul ion trap allows us to search for weak electric fields induced by light dark matter with masses around the neV range. Furthermore, we illustrate that an entangled qubit system involving N ions can enhance the excitation rate by a factor of N2. The sensitivities of the Paul ion trap system to axion-photon coupling and gauge kinetic mixing can reach previously unexplored parameter space.

Building and characterizing a stylus ion-trap system

Cold trapped ions can be excellent sensors for ultra-precision detection of physical quantities, which strongly depends on the measurement situation at hand. The stylus ion trap, formed by two concentric cylinders over a ground plane, holds the promise of relatively simple structure and larger solid angle for optical access and fluorescence collection in comparison with the conventional ion traps. Here we report our fabrication and characterization of the first stylus ion trap constructed in China, aiming for studying quantum optics and sensing weak electric fields in the future. We have observed the stable confinement of the ion in the trapping potential for more than two hours and measured the heating rate of the trap to be dε/dt = 7.10 ± 0.13 meV/s by the Doppler recooling method. Our work starts a way to building practical quantum sensors with high efficiency of optical collection and with ultimate goal for contributing to future quantum information technology.

Research progress of heat transport in trapped-ion crystals

Heat transport is one of the most important research topics in physics. Especially in recent years, with the in depth study on single-molecule devices, heat transport in low-dimensional (i.e. one- and two-dimensional) microsystems has received more and more attention. In the research of Fermi-Pasta-Ulam crystals and harmonic crystals, it is widely accepted that heat conduction in low-dimensional system does not follow Fourier’s law. Due to the lack of the equipment that can directly measure heat current, it has been proven to be a challenging task to carry out relevant experiments. Ion crystal in ion trap is located in vacuum and does not exchange energy with the external environment. The crystal structure and temperature can be accurately controlled by electric field and optical field, providing an ideal experimental platform for studying thermal conduction in low-dimensional crystals in classical state or quantum state. Herein we summarize the recent theoretical research on thermal conduction in ion crystals, including the methods of calculating temperature distribution and steady-state heat current in one-dimensional, two-dimensional, and three-dimensional models, as well as the characteristics of heat current and temperature distribution under different ion crystal configurations. Because the nonlinear effect caused by the imbalance among three dimensions hinders the heat transport, the heat current in ion crystal is largest in the linear configuration while smallest in the zig-zag configuration. In addition, we also introduce the influence of disorder on the thermal conductivity of ion crystal, including the influence on the heat current across various ion crystal configurations such as the linear, the zig-zag and the helical configuration. Notably, the susceptibility of ion crystal to disorder increases with crystal size increasing. Specifically, the zig-zag ion crystal configuration exhibits the largest susceptibility to disorder, whereas the linear configuration is least affected. Finally, we provide a concise overview of experimental studies of the heat conduction in low-dimensional systems. Examination of the heat conduction in ion crystal offers a valuable insight into various cooling techniques employed in ion trap systems, including sympathetic cooling, electromagnetically induced transparency cooling, and polarization gradient cooling. Just like macroscopic thermal diodes made by thermal metamaterials, it is possible that the microscopic thermal diodes can also be made in low-dimensional systems.

A Radio-Frequency Ion Trap System for the Multi-Reflection Time-of-Flight Mass Spectrometer at SHANS and Its Offline Commissioning

To precisely measure atomic masses and select neutron-deficient isotopes produced by fusion evaporation reactions, an MRTOF-MS (multi-reflection time-of-flight mass spectrometer) at the SHANS (Spectrometer for Heavy Atom and Nuclear Structure) is being developed. One of the key parts, an RF ion trap system with the aim to provide brilliant ion pulses with a low energy spread and narrow pulse width for ion preparation prior to injection into the MRTOF mass analyzer, has been constructed and commissioned offline successfully. The principle, construction details and test results are reported. Pulsed beams of 39K1+, 85,87Rb1+ and 133Cs1+ ions have been tested and the amplitudes and frequencies of the RF signals, DC voltages, helium gas pressure and time parameters have been scanned. The corresponding time spreads have reached 0.252 µs, 0.394 µs and 0.450 µs, respectively.

Cryogenic ion trap system for high-fidelity near-field microwave-driven quantum logic

We report the design, fabrication, and characterization of a cryogenic ion trap system for the implementation of quantum logic driven by near-field microwaves. The trap incorporates an on-chip microwave resonator with an electrode geometry designed to null the microwave field component that couples directly to the qubit, while giving a large field gradient for driving entangling logic gates. We map the microwave field using a single 43Ca+ ion, and measure the ion trapping lifetime and motional mode heating rates for one and two ions.

Quantum Computation of Hydrogen Bond Dynamics and Vibrational Spectra.

Calculating observable properties of chemical systems is often classically intractable and widely viewed as a promising application of quantum information processing. Here, we introduce a new framework for solving generic quantum chemical dynamics problems using quantum logic. We experimentally demonstrate a proof-of-principle instance of our method using the QSCOUT ion-trap quantum computer, where we experimentally drive the ion-trap system to emulate the quantum wavepacket dynamics corresponding to the shared-proton within an anharmonic hydrogen bonded system. Following the experimental creation and propagation of the shared-proton wavepacket on the ion-trap, we extract measurement observables such as its time-dependent spatial projection and its characteristic vibrational frequencies to spectroscopic accuracy (3.3 cm-1 wavenumbers, corresponding to >99.9% fidelity). Our approach introduces a new paradigm for studying the chemical dynamics and vibrational spectra of molecules and opens the possibility to describe the behavior of complex molecular processes with unprecedented accuracy.

A cryogenic ion trap for single molecule vibrational spectroscopy.

We report on an ion trapping system for performing a novel form of cryogenic messenger spectroscopy with single molecule sensitivity. The system features a cryogenic radio-frequency ion trap loaded with single analyte molecules via a quadrupole mass filter. We demonstrate the ability to controllably attach inert gas particles to buffer gas cooled, trapped molecular ions. Sympathetic cooling by co-trapped, laser cooled 88Sr+ further reduces the translational temperature of trapped molecules to the millikelvin regime. We verify the presence of cryogenic "tags" via non-destructive optical mass spectrometry and selectively remove these adducts by resonantly driving vibrational transitions in the tagged molecular ions. This enables us to derive the vibrational spectrum of a single analyte molecule from the frequency dependence of the tag detachment rate. We have demonstrated these capabilities by measuring transitions in the C-H stretching region for single cationic fragments of both indole (C8H7N) and 1,3-benzodioxole (C6H4O2CH2). These capabilities are not reliant on a specific molecular level structure and thus constitute a general, non-destructive method for vibrational spectroscopy of individual molecular ions.

Retraction Note: Quantum Information Splitting of an Arbitrary Three-Ion State in Ion-Trap System

Retraction Note: Quantum Information Splitting of an Arbitrary Three-Ion State in Ion-Trap System

Retraction Note: Controlled Teleportation of an Arbitrary Three-ion State in Ion-trap Systems

Retraction Note: Controlled Teleportation of an Arbitrary Three-ion State in Ion-trap Systems

Qubit dynamics driven by dipole field in thermal noise environment

Quantum computing is a new way to process quantum information by using superposition and entanglement of the quantum system. Quantum state’s vast Hilbert space allows it to perform operations that classical computers cannot. The quantum computing has unique advantages in dealing with some complex problems, so it has attracted wide attention. Computing a single qubit is the first of seven fundamental stages needed to achieve a large-scale quantum computer that is universal, scalable and fault-tolerant. In other words, the primary task of quantum computing is the careful preparation and precise regulation of qubits. At present, the physical systems that can be used as qubits include superconducting qubits, semiconductor qubits, ion trap systems and nitrogen-vacancy (NV) color centers. These physical systems have made great progress of decoherence time and scalability. Owing to the vulnerability of qubits, ambient thermal noise can cause quantum decoherence, which greatly affects the fidelity of qubits. Improving the fidelity of qubits is therefore a key step towards large-scale quantum computing. Based on the dipole field driven qubit, the stochastic dynamic structure decomposition method is adopted and the Kubo-Einstein fluctuation-dissipation theorem is used to study the qubit control in a thermal noise environment. The dipole field has components in three directions, not just in one plane, which allows more flexible control of quantum states. Without considering the noise, the quantum state can reach the target state 100%. In the noisy environment, thermal noise will cause the deviation between the actual final state and the target final state caused by thermal fluctuation, which becomes the main factor affecting the quantum fidelity. The influence of thermal noise is related to temperature and the evolution trajectory of quantum state. Therefore, this paper proposes an optimal scheme to improve the qubit fidelity in the thermal noise environment. The feasibility of this method is verified by numerical calculation, which can provide a new solution for further guiding and evaluating the experiment. The scheme is suitable for qubit systems of various physical control fields, such as semiconductor qubits and nitrogen vacancy center qubits. This work may have more applications in the development of quantum manipulation technology and can also be extended to multi-qubit systems, the details of which will appear in the future work.

Quantitative assessment and suppression of anharmonic potential of quadrupole linear radiofrequency ion traps with round electrodes

Precision manipulation of the quantum coherence of radiofrequency (RF) ion trap systems is one of the most important prerequisites for the development of high-performance ion frequency standards, high-fidelity ion trap quantum computing, and ion precision spectroscopy. The anharmonic potential of the ion trap exacerbates the non-ideal kinetic properties of the trapped ions and the simple harmonic motions of the heated ions, which in turn constrain the coherence time of the trapped ion systems. In this study, we developed a precision assessment and optimization method for the potential field of a quadrupole linear RF ion trap with round electrodes based on the joint weight suppression of the multi-order anharmonic potential, which is applicable for ion ensembles of cloud, liquid, and crystalline forms, and for different ion numbers. By quantifying the potential of each radial order of the decoupled transient RF potential, we established the quantitative loss relationship between the structure parameter of the linear RF ion trap with round electrodes and the trapping potential and outlined the influence of the structure parameter of the trap on the weight of the anharmonic potential. We determined the optimal structure parameter k (the ratio of pole radius re to radius r0 of the maximum trapping field) of the quadrupole linear ion trap with round electrodes as 1.1451447, which minimizes the overall anharmonic potential and achieves the highest reported accuracy (Reuben et al., 1996) [1]. This result provides a basis for the solution of problems in physics such as obtaining long-time trapping under low heating rate, precision manipulation of coherence, motion effect suppression, and efficient cooling of 3D ion systems, which are conducive to quantum coherence with time delays, spectral measurement approaching the theoretical accuracy limit, and high-performance frequency standards of 3D ion systems.

Development of low power and high voltage RF signal generator

Ion confinement technology can be widely used in quantum computation and precision measurement. In ion trapping system, ions are stably trapped in ion trap by the action of external forces.Multi-ion confinement requires the joint action of electric field and magnetic field to make the trapped ions overcome the interaction force between ions and be stably confined in the same specific space. Therefore, the stability of the electric force and the magnetic force determines the stability of ion confinement. Although the electric field and magnetic field provided by traditional commercial instruments is stable, it is not conducive to the miniaturization of the device. According to the previous experiment of ion confinement, we have designed a radio frequency(RF) signal generator that can provide continuous low power and stable high voltage RF electric field for multi-ion confinement system to guarantee the stability of trapped ions in quadrupole linear ion trap, also to improve the tapped ions density.

Squeezing-enhanced parameter estimation with a hybrid spin-oscillator interferometer

Inspired by the recent work [Nature (London) 521, 336 (2015)], we propose a scheme to suppress the backaction-induced dephasing of the spin state in a spin-oscillator system by squeezing the quantum fluctuation of the two-mode oscillator. We show specifically that squeezing either on a single mode individually or on both modes simultaneously could be used to effectively suppress spin dephasing. Therefore, with a spin-oscillator interferometer input by the spin-dependent squeezing cat state, the sensitivity of the rotational parameter estimation can be significantly enhanced. Given that various squeezings on the two-mode vibrations of the oscillator have been experimentally demonstrated, the proposal could provide a possibility to implement the sensitive parameter estimation, particularly in the ion-trap system.

Laser-cooled 171Yb+ microwave frequency standard with a short-term frequency instability of 8.5 × 10-13/√τ.

We report on the development of a microwave frequency standard based on a laser-cooled 171 Y b + ion trap system. The electronics , lasers, and magnetic shields are integrated into a single physical package. With over 105 ions are stably trapped, the system offers a high signal-to-noise ratio Ramsey line-shape. In comparison with previous work, the frequency instability of a 171 Y b + microwave clock was further improved to 8.5×10-13/τ for averaging times between 10 and 1000 s. Essential systematic shifts and uncertainties are also estimated.

Similarities and dissimilarities in the fragmentation of polycyclic aromatic hydrocarbon cations: A case study involving three dibenzopyrene isomers

The photon induced fragmentation behavior of the cations of three dibenzopyrene (C24H14) isomers (DBPae, DBPah and DBPal) is studied in a series of systematic mass spectrometric experiments. The ions are collected in an ion trap system and irradiated with different numbers of photons before being released into a time-of-flight mass spectrometer. The resulting mass spectra show a number of remarkable similarities, despite the structural differences between the three precursor species. Differences in the fragmentation patterns are found as well. Whereas it is not straight forward to explain the molecular origin of these findings, it is clear that the observed fragmentation patterns are relevant to further interpret the molecular composition of the interstellar medium (ISM), in which PAHs are omnipresent and subject to intense radiation. The main conclusion of this work is that PAHs comparable to the one studied here, may enrich the ISM with pure carbon species, Cn+, with n values roughly between 11 and 15, following a top-down approach.

Advances in the study of ion trap structures in quantum computation and simulation

Ion trap system is one of the main quantum systems to realize quantum computation and simulation. Various ion trap research groups worldwide jointly drive the continuous enrichment of ion trap structures, and develop a series of high-performance three-dimensional ion trap, two-dimensional ion trap chip, and ion traps with integrated components. The structure of ion trap is gradually developing towards miniaturization, high-optical-access and integration, and is demonstrating its outstanding ability in quantum control. Ion traps are able to trap increasingly more ions and precisely manipulate the quantum state of the system. In this review, we will summarize the evolution history of the ion trap structures in the past few decades, as well as the latest advances of trapped-ion-based quantum computation and simulation. Here we present a selection of representative examples of trap structures. We will summarize the progresses in the processing technology, robustness and versatility of ion traps, and make prospects for the realization of scalable quantum computation and simulation based on ion trap system.

Advances in the study of ion trap structures in quantum computation and simulation

Ion trap system is one of the main quantum systems to realize quantum computation and simulation. Various ion trap research groups worldwide jointly drive the continuous enrichment of ion trap structures, and develop a series of high-performance three-dimensional ion trap, two-dimensional ion trap chip, and ion traps with integrated components. The structure of ion trap is gradually developing towards miniaturization, high-optical-access and integration, and is demonstrating its outstanding ability in quantum control. Ion traps are able to trap increasingly more ions and precisely manipulate the quantum state of the system. In this review, we will summarize the evolution history of the ion trap structures in the past few decades, as well as the latest advances of trapped-ion-based quantum computation and simulation. Here we present a selection of representative examples of trap structures. We will summarize the progresses in the processing technology, robustness and versatility of ion traps, and make prospects for the realization of scalable quantum computation and simulation based on ion trap system.