arXiv subjects

Shoham Jacoby

Publications and source records attributed to Shoham Jacoby.

5 recordsLinked to original sources

arXiv2026

Fault-tolerant distributed quantum computing with a single nucleus per node

Distributed quantum computing interconnects small, high-quality nodes through optical links, but this architecture carries a pronounced asymmetry: in-node gates and measurements are cheap and high-fidelity, whereas inter-node communication relies on a low-coherence communication qubit and faulty photonics. Previous approaches overcame the noisy link by placing several high-quality data qubits in each node and consuming them for Bell pair and GHZ state distillation. Here we show that distillation can be avoided altogether. The key observation is that we can engineer a communication error bias, where photonic Bell pairs suffer frequent phase errors but only rare bit-flip errors. We design the syndrome-extraction circuits so that this phase noise appears solely as a measurement error that does not propagate to the data qubits, and is therefore suppressed by simply repeating the measurement; letting the error-correcting code itself, rather than a dedicated distillation subroutine, to purify the link. This dramatically reduces the need for ancillary nuclei: Floquet codes require only a single data qubit per node, while general stabilizer codes require just one additional ancilla. We demonstrate high error-correction thresholds throughout this regime, and we identify lattice surgery as inherently robust for this setting, enabling logical operations at a threshold close to that of quantum memory. As a result, the performance of the quantum computer is limited by the high-quality data qubits, while the requirements on photon indistinguishability and coherence of the communication qubit are substantially relaxed.

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arXiv2026

Stairway Codes: Floquetifying Bivariate Bicycle Codes and Beyond

Floquet codes define fault-tolerant protocols through periodic measurement sequences that drive a dynamically evolving stabilizer group. They provide a natural framework for hardware supporting two-qubit parity measurements but no unitary entangling gates. However, few known constructions achieve both high encoding rates and high thresholds. We close this gap by introducing Stairway codes, a family of high-rate Floquet protocols obtained by Floquetifying Abelian two-block group algebra codes, a class that includes the bivariate bicycle codes. By representing the static code as a foliated ZX-calculus network within a $(w{-}1)$-dimensional space-time lattice and rotating the time axis, we decompose its weight-$w$ stabilizers into a periodic sequence of pairwise measurements. This reduces the design of new codes within this family to the selection of favorable periodic boundary conditions. We identify instances with competitive parameters, analyze their distance under circuit-level noise, and demonstrate logical error rates surpassing those of other Floquet codes at comparable encoding rates. Remarkably, our construction requires fewer than 300 physical qubits to match the distance and encoding rate of semi-hyperbolic Floquet codes that use over 1300 qubits.

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arXiv2025

Magic State Injection with Erasure Qubits

Erasure qubits constitute a promising approach for tackling the daunting resources required for fault-tolerant quantum computing. By heralding erasure errors, both the error-correction threshold and the sub-threshold scaling of the logical error rate are significantly improved. While previous research has focused primarily on fault-tolerant quantum memories, we extend this investigation to magic state injection--a critical yet resource-intensive component of fault-tolerant quantum computation. We show that, after postselecting on erasures, the logical error rate of the injected magic state is set by the residual Pauli error, while the space-time overhead is only marginally increased as compared to non-erasure qubits with a similar noise strength. These conclusions hold both for injection into the surface code, and for injection and cultivation on the color code. For the former, we show that most of the gains can be achieved by using just three strategically placed erasure qubits in the surface code patch, independent of the patch size. For the latter, in contrast, it is beneficial to have all the qubits in the cultivation patch be erasure qubits. Our results for cultivation suggest that algorithmically relevant logical error rates may be within reach without magic state distillation for erasure rates $\lesssim 4\times 10^{-3}$ and residual Pauli error rates $\sim 10^{-4}$.

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arXiv2025

Hardware-Efficient Entanglement Distillation Using Bosonic Systems

High-fidelity entanglement shared between distant quantum systems is an essential resource for quantum communication and computation. Entanglement distillation addresses this need by converting multiple noisy Bell pairs into fewer higher-fidelity pairs, using only local quantum operations and classical communication. However, this approach typically requires a substantial overhead in the number of qubits. To bypass this hurdle, we propose to leverage the high-dimensional Hilbert space of a single pair of bosonic systems to store a large amount of entanglement, replacing the need for multi-qubit systems. To distill entanglement in such a setup, we devise a new entanglement distillation protocol, tailored for bosonic systems. The protocol converts a highly-entangled noisy state between two bosonic systems into a lower-dimensional but high-fidelity entangled state, using only local bosonic operations. We show that our protocol significantly enhances the fidelity of the entangled state in the presence of naturally occurring loss and dephasing errors. Compared to methods relying on multiple Bell pairs, our scheme offers a more hardware-efficient strategy, providing a practical route toward the realization of entanglement distillation.

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arXiv2025

Efficient Magic State Cultivation on the Surface Code

Magic state cultivation is a leading approach for generating the resource states required for fault-tolerant quantum computation. Here we present a new cultivation protocol that increases the success probability of magic-state generation in platforms with flexible and non-local connectivity. Our method implements cultivation directly on the surface code, avoiding the detour through alternative, less efficient error-correcting codes used in prior approaches. This both improves the acceptance rate and preserves compatibility with the geometry of the code and the hardware. Numerical simulations show that our protocols improve success probabilities and reduce output error rates compared with protocols tailored to locally connected platforms. Under realistic noise models for cold-atom and trapped-ion systems, we improve the rate of magic state generation by more than a factor of 20. Finally, we study qubit loss and erasure, and show that very low error rates can be achieved with minimal overhead, reaching below $10^{-6}$ infidelity using only nine physical erasure qubits.

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