Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression
Cat qubits, a type of bosonic qubit encoded in a harmonic oscillator, can exhibit an exponential noise bias against bit-flip errors with increasing mean photon number. Here, we focus on cat qubits stabilized by two-photon dissipation, where pairs of photons are added and removed from a harmonic osci...
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| Format: | Article |
| Language: | English |
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American Physical Society
2025-03-01
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| Series: | Physical Review X |
| Online Access: | http://doi.org/10.1103/PhysRevX.15.011070 |
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| author | Harald Putterman Kyungjoo Noh Rishi N. Patel Gregory A. Peairs Gregory S. MacCabe Menyoung Lee Shahriar Aghaeimeibodi Connor T. Hann Ignace Jarrige Guillaume Marcaud Yuan He Hesam Moradinejad John Clai Owens Thomas Scaffidi Patricio Arrangoiz-Arriola Joe Iverson Harry Levine Fernando G. S. L. Brandão Matthew H. Matheny Oskar Painter |
| author_facet | Harald Putterman Kyungjoo Noh Rishi N. Patel Gregory A. Peairs Gregory S. MacCabe Menyoung Lee Shahriar Aghaeimeibodi Connor T. Hann Ignace Jarrige Guillaume Marcaud Yuan He Hesam Moradinejad John Clai Owens Thomas Scaffidi Patricio Arrangoiz-Arriola Joe Iverson Harry Levine Fernando G. S. L. Brandão Matthew H. Matheny Oskar Painter |
| author_sort | Harald Putterman |
| collection | DOAJ |
| description | Cat qubits, a type of bosonic qubit encoded in a harmonic oscillator, can exhibit an exponential noise bias against bit-flip errors with increasing mean photon number. Here, we focus on cat qubits stabilized by two-photon dissipation, where pairs of photons are added and removed from a harmonic oscillator by an auxiliary, lossy buffer mode. This process requires a large loss rate and strong nonlinearities of the buffer mode that must not degrade the coherence and linearity of the oscillator. In this work, we show how to overcome this challenge by coloring the loss environment of the buffer mode with a multipole filter and optimizing the circuit to take into account additional inductances in the buffer mode. Using these techniques, we achieve near-ideal enhancement of cat-qubit bit-flip times with increasing photon number, reaching over 0.1 s with a mean photon number of only 4. Concurrently, our cat qubit remains highly phase coherent, with phase-flip times corresponding to an effective lifetime of T_{1,eff}≃70 μs, comparable with the bare oscillator lifetime. We achieve this performance even in the presence of an ancilla transmon, used for reading out the cat-qubit states, by engineering a tunable oscillator-ancilla dispersive coupling. Furthermore, the low nonlinearity of the harmonic oscillator mode allows us to perform pulsed cat-qubit stabilization, an important control primitive, where the stabilization can remain off for a significant fraction (e.g., two-thirds) of a 3 μs cycle without degrading bit-flip times. These advances are important for the realization of scalable error correction with cat qubits, where large noise bias and low phase-flip error rate enable the use of hardware-efficient outer error-correcting codes. |
| format | Article |
| id | doaj-art-1d2714ea1a084bef954df3a8be323e8d |
| institution | Kabale University |
| issn | 2160-3308 |
| language | English |
| publishDate | 2025-03-01 |
| publisher | American Physical Society |
| record_format | Article |
| series | Physical Review X |
| spelling | doaj-art-1d2714ea1a084bef954df3a8be323e8d2025-08-20T03:40:25ZengAmerican Physical SocietyPhysical Review X2160-33082025-03-0115101107010.1103/PhysRevX.15.011070Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip SuppressionHarald PuttermanKyungjoo NohRishi N. PatelGregory A. PeairsGregory S. MacCabeMenyoung LeeShahriar AghaeimeibodiConnor T. HannIgnace JarrigeGuillaume MarcaudYuan HeHesam MoradinejadJohn Clai OwensThomas ScaffidiPatricio Arrangoiz-ArriolaJoe IversonHarry LevineFernando G. S. L. BrandãoMatthew H. MathenyOskar PainterCat qubits, a type of bosonic qubit encoded in a harmonic oscillator, can exhibit an exponential noise bias against bit-flip errors with increasing mean photon number. Here, we focus on cat qubits stabilized by two-photon dissipation, where pairs of photons are added and removed from a harmonic oscillator by an auxiliary, lossy buffer mode. This process requires a large loss rate and strong nonlinearities of the buffer mode that must not degrade the coherence and linearity of the oscillator. In this work, we show how to overcome this challenge by coloring the loss environment of the buffer mode with a multipole filter and optimizing the circuit to take into account additional inductances in the buffer mode. Using these techniques, we achieve near-ideal enhancement of cat-qubit bit-flip times with increasing photon number, reaching over 0.1 s with a mean photon number of only 4. Concurrently, our cat qubit remains highly phase coherent, with phase-flip times corresponding to an effective lifetime of T_{1,eff}≃70 μs, comparable with the bare oscillator lifetime. We achieve this performance even in the presence of an ancilla transmon, used for reading out the cat-qubit states, by engineering a tunable oscillator-ancilla dispersive coupling. Furthermore, the low nonlinearity of the harmonic oscillator mode allows us to perform pulsed cat-qubit stabilization, an important control primitive, where the stabilization can remain off for a significant fraction (e.g., two-thirds) of a 3 μs cycle without degrading bit-flip times. These advances are important for the realization of scalable error correction with cat qubits, where large noise bias and low phase-flip error rate enable the use of hardware-efficient outer error-correcting codes.http://doi.org/10.1103/PhysRevX.15.011070 |
| spellingShingle | Harald Putterman Kyungjoo Noh Rishi N. Patel Gregory A. Peairs Gregory S. MacCabe Menyoung Lee Shahriar Aghaeimeibodi Connor T. Hann Ignace Jarrige Guillaume Marcaud Yuan He Hesam Moradinejad John Clai Owens Thomas Scaffidi Patricio Arrangoiz-Arriola Joe Iverson Harry Levine Fernando G. S. L. Brandão Matthew H. Matheny Oskar Painter Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression Physical Review X |
| title | Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression |
| title_full | Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression |
| title_fullStr | Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression |
| title_full_unstemmed | Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression |
| title_short | Preserving Phase Coherence and Linearity in Cat Qubits with Exponential Bit-Flip Suppression |
| title_sort | preserving phase coherence and linearity in cat qubits with exponential bit flip suppression |
| url | http://doi.org/10.1103/PhysRevX.15.011070 |
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