Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Log inSign up
Challenges
Datasets
Workspaces
Papers
Discussions
Leaderboard
Blog
Job Board
Q3AS

© 2026 Aqora Quantum S.A.S.

TermsPrivacyLegal Notice

Quantum 2.0 Conference and Exhibition

Highly fault-tolerant quantum computing using both discrete and continuous variables of light

Hyunseok Jeong, Seok-Hyung Lee, S. Omkar, Yong Siah Teo

Published Jan 1, 2023• 0 citations
Publisher

Abstract

Fault-tolerant photonic quantum computing schemes have suffered low photon-loss thresholds and heavy resource requirements particularly when using single-photon qubits. Recently, several approaches utilizing both discrete and continuous variables of light have been proposed to reach high photon-loss thresholds with relatively low resource requirements. Here we present two schemes that outperform known previous schemes in terms of photon-loss thresholds and resource overheads. The first one is a hybrid scheme that combines discrete-variable (DV) and continuous-variable (CV) states of light. This scheme is nearly ballistic in the sense that passive measurements with hybrid entangled states are sufficient with little feedforwards. The second scheme is based on the parity-based encoding and Bayesian error tracking that enables one to reach a significantly high photon-loss threshold of ~8.5% with moderate resource requirements compared to previous known schemes.

DOI
10.1364/quantum.2023.qtu4a.6

Related papers

High-Threshold Fusion-Based Quantum Computation with Optical Hybrid Qubits

Seong-Yeop Lim, Jaehak Lee, Nuri Kang +1 more

Hybrid discrete- and continuous-variable (DV-CV) encodings have been developed to overcome operational drawbacks of each individual encoding, while fusion-based quantum computation (FBQC) has emerged to address the practical challenges of scalability toward fault-tolerant photonic quantum computation. Here we introduce hybrid FBQC using small optical DV-CV hybrid resource states connected through hybrid fusions, to combine the advantages of both approaches. We develop protocols for directly generating these resource states without requiring local hybrid logic such as the Hadamard gate, together with a tailored decoding strategy that exploits the error information contained in individual hybrid-fusion outcomes. We demonstrate that hybrid FBQC achieves a photon loss threshold of 2.231% while requiring only 12 hybrid fusions per surface-code unit cell, substantially improving upon the 0.89% threshold and 60-fusion requirement of previous hybrid measurement-based scheme. These results establish optical hybrid FBQC as a high-threshold resource-efficient route to scalable fault-tolerant photonic quantum computation.

quant-pharXiv:2610.38914•Oct 30, 2026•0 citations

Fault-Tolerant Quantum Computation by Hybrid Qubits with Bosonic Cat Code and Single Photons

Jaehak Lee, Nuri Kang, Seok-Hyung Lee +3 more

Hybridizing different degrees of freedom or physical platforms potentially offers various advantages in building scalable quantum architectures. Here, we introduce a fault-tolerant hybrid quantum computation by building on the advantages of both discrete-variable (DV) and continuous-variable (CV) systems. In particular, we define a CV-DV hybrid qubit with a bosonic cat code and a single photon, which is implementable in current photonic platforms. Due to the cat code encoded in the CV part, the predominant loss errors are readily correctable without multiqubit encoding, while the logical basis is inherently orthogonal due to the DV part. We design fault-tolerant architectures by concatenating hybrid qubits and an outer DV quantum error-correction code such as a topological code, exploring their potential merit in developing scalable quantum computation. We demonstrate by numerical simulations that our scheme is at least an order of magnitude more resource efficient compared to all previous proposals in photonic platforms, allowing us to achieve a record-high loss threshold among existing CV and hybrid approaches. We discuss the realization of our approach not only in all-photonic platforms but also in other hybrid platforms including superconducting and trapped-ion systems, which allows us to find various efficient routes toward fault-tolerant quantum computing. Published by the American Physical Society 2024

arXiv:2401.00450•PRX Quantum•Aug 2, 2024•20 citations

Photonic hybrid quantum computing

Jaehak Lee, S. Omkar, Yong Siah Teo +4 more

Photons are a ubiquitous carrier of quantum information: they are fast, suffer minimal decoherence, and do not require huge cryogenic facilities. Nevertheless, their intrinsically weak photon-photon interactions remain a key obstacle to scalable quantum computing. This review surveys hybrid photonic quantum computing, which exploits multiple photonic degrees of freedom to combine the complementary strengths of discrete and bosonic encodings, thereby significantly mitigating the challenge of weak photon-photon interactions. We first outline the basic principles of discrete-variable, native continuous-variable, and bosonic-encoding paradigms. We then summarize recent theoretical advances and state-of-the-art experimental demonstrations with a particular emphasis on the hybrid approach. Its unique advantages, such as efficient generation of resource states and nearly ballistic (active-feedforward-free) operations, are highlighted alongside the remaining technical challenges. To facilitate a clear comparison, we explicitly present the error thresholds and resource overheads required for fault-tolerant quantum computing. Our work offers a focused overview that clarifies how the hybrid approach enables scalable and compatible architectures for quantum computing.

arXiv:2510.00534•Newton•Dec 30, 2025•2 citations

Resource-Efficient Topological Fault-Tolerant Quantum Computation with Hybrid Entanglement of Light

S. Omkar, Yong Siah Teo, Hyunseok Jeong

We propose an all-linear-optical scheme to ballistically generate a cluster state for measurement-based topological fault-tolerant quantum computation using hybrid photonic qubits entangled in a continuous-discrete domain. Availability of near-deterministic Bell-state measurements on hybrid qubits is exploited for this purpose. In the presence of photon losses, we show that our scheme leads to a significant enhancement in both tolerable photon-loss rate and resource overheads. More specifically, we report a photon-loss threshold of $\ensuremath{\sim}3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which is higher than those of known optical schemes under a reasonable error model. Furthermore, resource overheads to achieve logical error rate of ${10}^{\ensuremath{-}6}({10}^{\ensuremath{-}15})$ is estimated to be $\ensuremath{\sim}8.5\ifmmode\times\else\texttimes\fi{}{10}^{5}(1.7\ifmmode\times\else\texttimes\fi{}{10}^{7})$, which is significantly less by multiple orders of magnitude compared to other reported values in the literature.

arXiv:1906.04864•Physical Review Letters•Aug 4, 2020•49 citations

Hybrid and Fusion Approach for Fault-tolerant Quantum Computing

Jaehak LEE, Wooyeong SONG

Quantum error correction is an essential tool for performing reliable quantum information processing tasks under noisy circumstances, and is attracting growing attention today as a crucial element for realizing the fault-tolerant quantum computer. In this article, we introduce two cutting-edge quantum error correction techniques for implementing fault-tolerant quantum computation: the hybrid approach and the fusion-based quantum computation. The hybrid quantum computing utilizes hybrid qubits which combine the advantages of continuous-variable and discrete-variable qubits. The fusion-based quantum error correction offers a way, specialized for photonic quantum information processing, toward fault tolerance based on two-qubit measurement, known as fusion. We demonstrate by numerical simulations that our methods achieve the increased loss threshold and the improved resource efficiency compared to previous photonic proposals.

Physics and High Technology•Oct 31, 2024•0 citations

Highly photon-loss-tolerant quantum computing using hybrid qubits

S. Omkar, Yong Siah Teo, Seung-Woo Lee +1 more

We investigate a scheme for topological quantum computing using optical hybrid qubits and make an extensive comparison with previous all-optical schemes. We show that the photon loss threshold reported by Omkar et al. [Phys. Rev. Lett. 125, 060501 (2020)] can be improved further by employing postselection and multi-Bell-state-measurement-based entangling operations to create a special cluster state, known as Raussendorf lattice for topological quantum computation. In particular, the photon loss threshold is enhanced up to $5.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which is the highest reported value given a reasonable error model. This improvement is obtained at the price of consuming more resources by an order of magnitude compared with the scheme in the aforementioned reference. Nevertheless, this scheme remains resource-efficient compared with other known optical schemes for fault-tolerant quantum computation.

arXiv:2011.04209•Physical Review A•Mar 9, 2021•22 citations
Fault-tolerant photonic quantum computing schemes have suffered low photon-loss thresholds and heavy resource requirements particularly when using single-photon qubits. Recently, several approaches utilizing both discrete and continuous variables of light have been proposed to reach high photon-loss thresholds with relatively low resource requirements. Here we present two schemes that outperform known previous schemes in terms of photon-loss thresholds and resource overheads. The first one is a hybrid scheme that combines discrete-variable (DV) and continuous-variable (CV) states of light. This scheme is nearly ballistic in the sense that passive measurements with hybrid entangled states are sufficient with little feedforwards. The second scheme is based on the parity-based encoding and Bayesian error tracking that enables one to reach a significantly high photon-loss threshold of ~8.5% with moderate resource requirements compared to previous known schemes.
Hybrid discrete- and continuous-variable (DV-CV) encodings have been developed to overcome operational drawbacks of each individual encoding, while fusion-based quantum computation (FBQC) has emerged to address the practical challenges of scalability toward fault-tolerant photonic quantum computation. Here we introduce hybrid FBQC using small optical DV-CV hybrid resource states connected through hybrid fusions, to combine the advantages of both approaches. We develop protocols for directly generating these resource states without requiring local hybrid logic such as the Hadamard gate, together with a tailored decoding strategy that exploits the error information contained in individual hybrid-fusion outcomes. We demonstrate that hybrid FBQC achieves a photon loss threshold of 2.231% while requiring only 12 hybrid fusions per surface-code unit cell, substantially improving upon the 0.89% threshold and 60-fusion requirement of previous hybrid measurement-based scheme. These results establish optical hybrid FBQC as a high-threshold resource-efficient route to scalable fault-tolerant photonic quantum computation.
Hybridizing different degrees of freedom or physical platforms potentially offers various advantages in building scalable quantum architectures. Here, we introduce a fault-tolerant hybrid quantum computation by building on the advantages of both discrete-variable (DV) and continuous-variable (CV) systems. In particular, we define a CV-DV hybrid qubit with a bosonic cat code and a single photon, which is implementable in current photonic platforms. Due to the cat code encoded in the CV part, the predominant loss errors are readily correctable without multiqubit encoding, while the logical basis is inherently orthogonal due to the DV part. We design fault-tolerant architectures by concatenating hybrid qubits and an outer DV quantum error-correction code such as a topological code, exploring their potential merit in developing scalable quantum computation. We demonstrate by numerical simulations that our scheme is at least an order of magnitude more resource efficient compared to all previous proposals in photonic platforms, allowing us to achieve a record-high loss threshold among existing CV and hybrid approaches. We discuss the realization of our approach not only in all-photonic platforms but also in other hybrid platforms including superconducting and trapped-ion systems, which allows us to find various efficient routes toward fault-tolerant quantum computing. Published by the American Physical Society 2024
Photons are a ubiquitous carrier of quantum information: they are fast, suffer minimal decoherence, and do not require huge cryogenic facilities. Nevertheless, their intrinsically weak photon-photon interactions remain a key obstacle to scalable quantum computing. This review surveys hybrid photonic quantum computing, which exploits multiple photonic degrees of freedom to combine the complementary strengths of discrete and bosonic encodings, thereby significantly mitigating the challenge of weak photon-photon interactions. We first outline the basic principles of discrete-variable, native continuous-variable, and bosonic-encoding paradigms. We then summarize recent theoretical advances and state-of-the-art experimental demonstrations with a particular emphasis on the hybrid approach. Its unique advantages, such as efficient generation of resource states and nearly ballistic (active-feedforward-free) operations, are highlighted alongside the remaining technical challenges. To facilitate a clear comparison, we explicitly present the error thresholds and resource overheads required for fault-tolerant quantum computing. Our work offers a focused overview that clarifies how the hybrid approach enables scalable and compatible architectures for quantum computing.
We propose an all-linear-optical scheme to ballistically generate a cluster state for measurement-based topological fault-tolerant quantum computation using hybrid photonic qubits entangled in a continuous-discrete domain. Availability of near-deterministic Bell-state measurements on hybrid qubits is exploited for this purpose. In the presence of photon losses, we show that our scheme leads to a significant enhancement in both tolerable photon-loss rate and resource overheads. More specifically, we report a photon-loss threshold of $\ensuremath{\sim}3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which is higher than those of known optical schemes under a reasonable error model. Furthermore, resource overheads to achieve logical error rate of ${10}^{\ensuremath{-}6}({10}^{\ensuremath{-}15})$ is estimated to be $\ensuremath{\sim}8.5\ifmmode\times\else\texttimes\fi{}{10}^{5}(1.7\ifmmode\times\else\texttimes\fi{}{10}^{7})$, which is significantly less by multiple orders of magnitude compared to other reported values in the literature.
Quantum error correction is an essential tool for performing reliable quantum information processing tasks under noisy circumstances, and is attracting growing attention today as a crucial element for realizing the fault-tolerant quantum computer. In this article, we introduce two cutting-edge quantum error correction techniques for implementing fault-tolerant quantum computation: the hybrid approach and the fusion-based quantum computation. The hybrid quantum computing utilizes hybrid qubits which combine the advantages of continuous-variable and discrete-variable qubits. The fusion-based quantum error correction offers a way, specialized for photonic quantum information processing, toward fault tolerance based on two-qubit measurement, known as fusion. We demonstrate by numerical simulations that our methods achieve the increased loss threshold and the improved resource efficiency compared to previous photonic proposals.
We investigate a scheme for topological quantum computing using optical hybrid qubits and make an extensive comparison with previous all-optical schemes. We show that the photon loss threshold reported by Omkar et al. [Phys. Rev. Lett. 125, 060501 (2020)] can be improved further by employing postselection and multi-Bell-state-measurement-based entangling operations to create a special cluster state, known as Raussendorf lattice for topological quantum computation. In particular, the photon loss threshold is enhanced up to $5.7\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}3}$, which is the highest reported value given a reasonable error model. This improvement is obtained at the price of consuming more resources by an order of magnitude compared with the scheme in the aforementioned reference. Nevertheless, this scheme remains resource-efficient compared with other known optical schemes for fault-tolerant quantum computation.