arXiv subjects

Matteo Marinelli

Publications and source records attributed to Matteo Marinelli.

13 recordsLinked to original sources

arXiv2026

A monolithic segmented 3D ion trap fabricated from fused silica by selective laser-induced etching

We present the design, fabrication, and characterization of a monolithic, segmented, three-dimensional linear Paul ion trap for quantum science applications. The trap is fabricated from a single fused-silica block using selective laser-induced etching (SLE) and is subsequently metallized, forming electrodes isolated by self-shadowing trench structures without the need for layer alignment or external shadow masks. The segmented electrodes allow for shaping of the axial potential, enabling the creation of anharmonic potential wells, such as those required for equidistant ion strings. In addition, they enable shuttling and splitting of ion chains. We discuss key design choices and SLE-imposed constraints on achievable feature sizes, and evaluate electron-beam evaporation and magnetron sputtering as metallization approaches. Across two independent experimental setups, we demonstrate stable trapping and control of linear chains of up to 33 $^{40}$Ca$^+$ ions, including approximately equally spaced configurations. The measured secular frequencies in both traps agree with boundary-element simulations at the percent level, with residual deviations attributed to stray electric fields in the presence of anharmonic axial potentials, rather than fabrication imperfections. We measure axial micromotion field strengths on the order of 100 V/m along the trap axis, in approximate agreement with simulations. For radial mode frequencies near 2 MHz and an ion-electrode distance of 300 um, we measure heating rates of the order of 10 quanta/s in all but one motional mode, which is elevated by a technical noise source. The presented trap design is thus suitable for a wide range of quantum science applications and demonstrates the viability of SLE for the fabrication of finely segmented, monolithic, three-dimensional ion traps.

physics.atom-ph↗

arXiv2026

State-dependent Gaussian gate set using an optical tweezer for trapped ions

We demonstrate a state-dependent Gaussian gate set on the motional modes of trapped $^{40}$Ca$^+$ ions, realized with an optical tweezer. Dynamic control of the tweezer intensity and position enables local displacement, squeezing, phase-space rotation, and beamsplitter operations, constituting a complete gate set. By varying the tweezer position relative to the ion, we show how the strength of each operation is set by the corresponding spatial derivative of the local optical potential. We further demonstrate the inherent dependence of each operation on the ion's internal state and use coherent spin-motion coupling provided by the tweezer to create a motional cat state. Our work establishes optical tweezers as a unified and local resource for continuous-variable quantum control in trapped ion systems.

quant-ph↗

arXiv2026

Direct observation of the optical Magnus effect with a trapped ion

We directly observe and spatially map an optical analog of the Magnus effect, where intrinsic spin-orbit-like coupling of light generates a spin-dependent transverse displacement of the atom-light interaction profile for a $^{40}$Ca$^+$ ion. Probed on a quadrupole transition using a tightly focused beam, we observe displacements of the maximum in the profile of the effective interaction by several 100 nm originating from intrinsic longitudinal electric field components beyond the paraxial approximation. The tight focus of the beam induces additional transverse polarization gradients, which we characterize through a phase-sensitive measurement and spatial maps for different beam configurations. The results establish the physical basis of polarization-gradient interactions relevant to optical tweezer-based quantum control.

physics.atom-ph↗

arXiv2025

Microsecond-scale high-survival and number-resolved detection of ytterbium atom arrays

Scalable atom-based quantum platforms for simulation, computing, and metrology require fast high-fidelity, low-loss imaging of individual atoms. Standard fluorescence detection methods rely on continuous cooling, limiting the detection range to one atom and imposing long imaging times that constrain the experimental cycle and mid-circuit conditional operations. Here, we demonstrate fast and low-loss single-atom imaging in optical tweezers without active cooling, enabled by the favorable properties of ytterbium. Collecting fluorescence over microsecond timescales, we reach single-atom discrimination fidelities above 99.9% and single-shot survival probabilities above 99.5%. Through interleaved recooling pulses, as short as a few hundred microseconds for atoms in magic traps, we perform tens of consecutive detections with constant atom-retention probability per image - an essential step toward fast atom re-use in tweezer-based processors and clocks. Our scheme does not induce parity projection in multiply-occupied traps, enabling number-resolved single-shot detection of several atoms per site. This allows us to study the near-deterministic preparation of single atoms in tweezers driven by blue-detuned light-assisted collisions. Moreover, the near-diffraction-limited spatial resolution of our low-loss imaging enables number-resolved microscopy in dense arrays, opening the way to direct site-occupancy readout in optical lattices for density fluctuation and correlation measurements in quantum simulators.

cond-mat.quant-gas↗

arXiv2025

Local vs non-local dynamics in cavity-coupled Rydberg atom arrays

Locality is a transversal principle that governs quantum dynamics of many-body systems. However, for cavity embedded systems, such fundamental notion is hindered by the presence of non-local cavity modes, leaving space for new possible dynamical behaviors. Here, we investigate the real-time dynamics of low-energy excitations in one dimensional Rydberg atom arrays coupled to a global cavity mode. We derive an effective description in terms of a Tavis-Cummings-Ising model, whose phase diagram features ordered and disordered phases. The non-local nature of the cavity mode drastically affects the emergent meson and string dynamics. Mesons hybridize coherently with the cavity photons, leading to composite meson-polaritons excitations. Strings, differently from local interacting theories, acquire a finite kinetic energy thanks to non-local cavity-mediated interactions between the underlying domain-walls. We then conclude by presenting a new concrete experimental blueprint for a cavity QED Rydberg atom array simulator where the physics outlined in this work can be realized.

quant-ph↗

arXiv2024

A high optical access cryogenic system for Rydberg atom arrays with a 3000-second trap lifetime

We present an optical tweezer array of $^{87}$Rb atoms housed in an cryogenic environment that successfully combines a 4 K cryopumping surface, a <50 K cold box surrounding the atoms, and a room-temperature high-numerical-aperture objective lens. We demonstrate a 3000 s atom trap lifetime, which enables us to optimize and measure losses at the $10^{-4}$ level that arise during imaging and cooling, which are important to array rearrangement. We perform both ground-state qubit manipulation with an integrated microwave antenna and two-photon coherent Rydberg control, with the local electric field tuned to zero via integrated electrodes. We anticipate that the reduced blackbody radiation at the atoms from the cryogenic environment, combined with future electrical shielding, should decrease the rate of undesired transitions to nearby strongly-interacting Rydberg states, which cause many-body loss and impede Rydberg gates. This low-vibration, high-optical-access cryogenic platform can be used with a wide range of optically trapped atomic or molecular species for applications in quantum computing, simulation, and metrology.

physics.atom-ph↗

arXiv2024

Quantifying Light-assisted Collisions in Optical Tweezers Across the Hyperfine Spectrum

We investigate the role of hyperfine structure in resonant-dipole interactions between two atoms cotrapped in an optical tweezer. Two-body loss rates from light-assisted collisions (LACs) are measured across the $^{87}$Rb hyperfine spectrum and connected to properties of molecular photoassociation potentials via a semiclassical model. To obtain our results, we introduce an imaging technique that leverages repulsive LACs to detect two atoms in a trap, thereby circumventing parity constraints in tweezers. Our findings offer key insights for exploiting hyperfine structure in laser-induced collisions to control cold atoms and molecules in a broad range of quantum science applications.

physics.atom-ph↗

arXiv2023

Low-excitation transport and separation of high-mass-ratio mixed-species ion chains

We demonstrate low-excitation transport and separation of two-ion crystals consisting of one beryllium and one calcium ion, with a high mass ratio of $4.4$. The full separation involves transport of the mixed-species chain, splitting each ion into separate potential wells, and then transport of each ion prior to detection. We find the high mass ratio makes the protocol sensitive to mode crossings between axial and radial modes, as well as to uncontrolled radial electric fields that induce mass-dependent twists of the ion chain. By controlling these stages, we achieve excitation as low as $\bar{n}=1.40 \pm 0.08$ phonons for the calcium ion and $\bar{n}=1.44 \pm 0.09$ phonons for the beryllium ion. Separation and transport of mixed-species chains are key elements of the QCCD architecture, and may also be applicable to quantum-logic-based spectroscopy of exotic species.

quant-ph↗

arXiv2023

Long-range-enhanced surface codes

The surface code is a quantum error-correcting code for one logical qubit, protected by spatially localized parity checks in two dimensions. Due to fundamental constraints from spatial locality, storing more logical qubits requires either sacrificing the robustness of the surface code against errors or increasing the number of physical qubits. We bound the minimal number of spatially nonlocal parity checks necessary to add logical qubits to a surface code while maintaining, or improving, robustness to errors. We saturate the lower limit of this bound, when the number of added logical qubits is a constant, using a family of hypergraph product codes, interpolating between the surface code and constant-rate low-density parity-check codes. Fault-tolerant protocols for logical gates in the quantum code can be inherited from its classical parent codes. We provide near-term practical implementations of this code for hardware based on trapped ions or neutral atoms in mobile optical tweezers. Long-range-enhanced surface codes outperform conventional surface codes using hundreds of physical qubits, and represent a practical strategy to enhance the robustness of logical qubits to errors in near-term devices.

quant-ph↗

arXiv2018

Encoding a qubit in a trapped-ion mechanical oscillator

The stable operation of quantum computers will rely on error-correction, in which single quantum bits of information are stored redundantly in the Hilbert space of a larger system. Such encoded qubits are commonly based on arrays of many physical qubits, but can also be realized using a single higher-dimensional quantum system, such as a harmonic oscillator. A powerful encoding is formed from a periodically spaced superposition of position eigenstates. Various proposals have been made for realizing approximations to such states, but these have thus far remained out of reach. Here, we demonstrate such an encoded qubit using a superposition of displaced squeezed states of the harmonic motion of a single trapped Calcium ion, controlling and measuring the oscillator through coupling to an ancilliary internal-state qubit. We prepare and reconstruct logical states with an average square fidelity of $87.3 \pm 0.7 \%$, and demonstrate a universal logical single qubit gate set which we analyze using process tomography. For Pauli gates we reach process fidelities of $\approx 97\%$, while for continuous rotations we use gate teleportation achieving fidelities of $\approx 89 \%$. The control demonstrated opens a route for exploring continuous variable error-correction as well as hybrid quantum information schemes using both discrete and continuous variables. The code states also have direct applications in quantum sensing, allowing simultaneous measurement of small displacements in both position and momentum.

quant-ph↗

arXiv2018

Repeated multi-qubit readout and feedback with a mixed-species trapped-ion register

Quantum error correction will be essential for realizing the full potential of large-scale quantum information processing devices. Fundamental to its experimental realization is the repetitive detection of errors via projective measurements of quantum correlations among qubits, and correction using conditional feedback. Performing these tasks repeatedly requires a system in which measurement and feedback decision times are short compared to qubit coherence times, where the measurement reproduces faithfully the desired projection, and for which the measurement process has no detrimental effect on the ability to perform further operations. Here we demonstrate up to 50 sequential measurements of correlations between two beryllium-ion qubits using a calcium ion ancilla, and implement feedback which allows us to stabilize two-qubit subspaces as well as Bell states. Multi-qubit mixed-species gates are used to transfer information from qubits to the ancilla, enabling quantum state detection with negligible crosstalk to the stored qubits. Heating of the ion motion during detection is mitigated using sympathetic recooling. A key element of the experimental system is a powerful classical control system, which features flexible in-sequence processing to implement feedback control. The methods employed here provide a number of essential ingredients for scaling trapped-ion quantum computing, and provide new opportunities for quantum state control and entanglement-enhanced quantum metrology.

quant-ph↗

arXiv2015

Parallel transport quantum logic gates with trapped ions

We demonstrate single-qubit operations by transporting a beryllium ion with a controlled velocity through a stationary laser beam. We use these to perform coherent sequences of quantum operations, and to perform parallel quantum logic gates on two ions in different processing zones of a multiplexed ion trap chip using a single recycled laser beam. For the latter, we demonstrate individually addressed single-qubit gates by local control of the speed of each ion. The fidelities we observe are consistent with operations performed using standard methods involving static ions and pulsed laser fields. This work therefore provides a path to scalable ion trap quantum computing with reduced requirements on the optical control complexity.

quant-ph↗

arXiv2014

Spin-motion entanglement and state diagnosis with squeezed oscillator wavepackets

Mesoscopic superpositions of distinguishable coherent states provide an analog to the Schr\"odinger's cat thought experiment. For mechanical oscillators these have primarily been realised using coherent wavepackets, for which the distinguishability arises due to the spatial separation of the superposed states. Here, we demonstrate superpositions composed of squeezed wavepackets, which we generate by applying an internal-state dependent force to a single trapped ion initialized in a squeezed vacuum state with 9 dB reduction in the quadrature variance. This allows us to characterise the initial squeezed wavepacket by monitoring the onset of spin-motion entanglement, and to verify the evolution of the number states of the oscillator as a function of the duration of the force. In both cases, we observe clear differences between displacements aligned with the squeezed and anti-squeezed axes. We observe coherent revivals when inverting the state-dependent force after separating the wavepackets by more than 19 times the ground-state root mean squared extent, which corresponds to 56 times the root mean squared extent of the squeezed wavepacket along the displacement direction. Aside from their fundamental nature, these states may be useful for quantum metrology or quantum information processing with continuous variables.

quant-ph↗