Helios: A 98-qubit trapped-ion quantum computer

TL;DR

Helios demonstrates a 98-qubit trapped-ion quantum computer built on a QCCD architecture with a four-way junction enabling all-to-all connectivity. The system pairs Ba+ qubits with sympathetic Yb+ cooling and a real-time runtime to map virtual to physical qubits, supporting dynamic programs and gate streaming. Component-level benchmarks yield $1Q$ infidelity $2.5\times10^{-5}$, $2Q$ infidelity $7.9\times10^{-4}$, and SPAM infidelity $4.8\times10^{-4}$, with system-level tests showing robust performance on random Clifford circuits and random circuit sampling beyond classical simulability. These results establish Helios as a leading near-term quantum processor at the scale of ~100 qubits and illustrate a viable path toward scalable, fault-tolerant trapped-ion quantum computation using junction-based QCCD architectures.

Abstract

We report on Quantinuum Helios, a 98-qubit trapped-ion quantum processor based on the quantum charge-coupled device (QCCD) architecture. Helios features $^{137}$Ba$^{+}$ hyperfine qubits, all-to-all connectivity enabled by a rotatable ion storage ring connecting two quantum operation regions by a junction, speed improvements from parallelized operations, and a new software stack with real-time compilation of dynamic programs. Averaged over all operational zones in the system, we achieve average infidelities of $2.5(1)\times10^{-5}$ for single-qubit gates, $7.9(2)\times10^{-4}$ for two-qubit gates, and $4.8(6)\times10^{-4}$ for state preparation and measurement, none of which are fundamentally limited and likely able to be improved. These component infidelities are predictive of system-level performance in both random Clifford circuits and random circuit sampling, the latter demonstrating that Helios operates well beyond the reach of classical simulation and establishes a new frontier of fidelity and complexity for quantum computers.

Figures (16)

• Figure 1: An image of 98 atomic ions illuminated by resonant laser light in the Helios 2D surface trap illustrated in Fig. \ref{['fig:MainFig']}. The overlaid lines indicate different regions of the device with the quincunx of ions showing the location of the ion trap junction.
• Figure 2: An illustration of the Helios design and conception of operations. (a) The final five stages of loading the cache region with qubits from ring storage. The ring rotates ions in both directions to move the circled qubit into the cache. (b) Diagram of trap (not to scale) part-way through a program, ring storage qubits are being loaded into the cache and qubits in the quantum logic region are undergoing ground-state cooling. The actual horizontal length is 15.3 mm, the ring diameter is 2.8 mm, and the operational zones are 750 $\mu$m apart. (c) Junction operations showing the retrieval and alignment of an ion crystal, and an ion crystal moving through the junction to stay in the ring storage. (d) The proper alignment of a 4-ion crystal in the quantum logic zones. (e) Laser beam and crystal configurations during example quantum operations as labeled. Beams are focused to operate on top/bottom legs as shown by color gradients. The 2Q gate beams are tilted both vertically and horizontally away from the 45 degree line that intersects the ion crystals in both legs by approximately 1 degree so to only interact with a single ion crystal at a time.
• Figure 3: Three types of measurements are available in all 8 quantum operation zones which make use of optical ($^2S_{1/2}$, $^2D_{5/2}$), metastable ($^2D_{5/2}$), and ground state ($^2S_{1/2}$) superpositions. All measurements are made with the target ion displaced from the RF null to reduce stray light interacting with non-measured ions Gaebler2021crosstalk as shown with double arrows. (a) Standard measurement occurs when the user specifies a measurement but not for all the qubits in the batch. (b) Protected measurement occurs when the compiler detects an entire batch of qubits will be measured, such as at the end-of-program measurement. Protected measurement performs the $^{2}D_{5/2}$ mapping operations on both qubits prior to state detection such that crosstalk from 493 nm detection light does not affect the measurement outcome. (c) User specified ternary measurement allows the user to obtain a result of 0, 1, or $L$, where $L$ indicates leakage out of the qubit manifold. In this case, each qubit state amplitude is mapped to different parts of the $^{2}D_{5/2}$ manifold Senko2025 and any remaining population in the $^2S_{1/2}$ population (representing leakage errors) is measured via induced fluorescence with the 493 nm and 650 nm lasers. Afterwards, a series of pulses independently maps each state amplitude back into the $^2S_{1/2}$ and $^2D_{3/2}$ manifolds allowing measurement of the qubit state (0 or 1). Ternary and protected measure can be combined when an entire batch is measured. (d) Energy level diagram for $^{137}$Ba$^+$ with $^2S_{1/2}$ ground state manifold used for storage and quantum operations, optical superpositions of $^2S_{1/2}$ and $^2D_{5/2}$ are used during standard measurement. An optical superposition shelves the qubit ground state $\vert 0 \rangle$ state to the $^2D_{5/2}$ manifold for measurement. (e) Metastable superpositions in the $^{2}D_{5/2}$ are used for ternary measurements by shelving both ground state qubit levels to detect leakage errors.
• Figure 4: (a) Time budget per layer for an example depth-10 random program that executes 1Q and 2Q gates on all 98 qubits after an arbitrary permutation each layer, broken down into three categories: ion transport; ground-state cooling; and quantum operations (1Q and 2Q gates). (b) Total time per layer versus number of active qubits for three programs: a random program with fully dense 2Q gates, the same random program with approximately half the 2Q gate density, and a program with 2D nearest-neighbor 2Q gate pairing. For the two random programs, solid points represent the mean of 10 program instances; hollow points show the individual values.
• Figure 5: 1QRB data: (a) 1QRB survival probability as a function of sequence length, for the 16 qubits occupying the 8 operation zones. (b) 1QRB measured leakage population as a function of sequence length. The leakage rate is combined with the survival decay rate to compute the 1Q Clifford infidelity. (c) Breakdown of 1Q Clifford error rates into computational (comp.) errors and leakage (leak.) errors, for the 16 individual qubits. Label locations correspond to qubit locations in Fig. \ref{['fig:MainFig']}b with qubits 0-7 in the top operation zones and 8-15 in the bottom (two per zone ordered left to right).