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Alice & Bob Boson 4 (chips 4A/4B/4C)
Alice & Bob Boson 4 (chips 4A/4B/4C) is a superconducting gate-based processor by Alice & Bob with a disclosed qubit count detailed below (2024). Below: every publicly disclosed figure with its source, method, and vendor-claim status — plus what is not disclosed, recorded as findings.
Measurement records6 disclosed · 1 not disclosed · 2 sources
Select a figure to open its record
Qubit count (qubit_count_physical)2 independent, uncoupled cat qubits per chip (operated as single-qubit chips); 3 chip backends: Boson 4A, 4B, 4C cat qubitsvendor claim
Vendor claim
- Method
- VENDOR_UNSPECIFIED
- Notes
- Research-class device: no two-qubit gates available, so no 2Q fidelity metric exists for this hardware.
- Citation key
[alice-bob/alice-bob-boson-4:qubit-count-physical:2026-08-19]
Bit flip lifetime (bit_flip_lifetime)830 us at average_nb_photons=4; 120 s at average_nb_photons=11 see valuevendor claim
Vendor claim
- Method
- operating-point dependent (average photon number of the cat state)
- Aggregation
- typical backend spec per operating point
- Notes
- Product page claims 'bit-flip lifetime exceeding 7 minutes... beats any other superconducting qubit' (https://alice-bob.com/products/quantum-cloud-felis/boson-4/); Google Cloud launch newsroom item cites 'up to 430 seconds'. Values differ by operating point, not a conflict. In Sept 2025 the company reported >1 hour bit-flip times on newer lab hardware (not Boson 4).
- Citation key
[alice-bob/alice-bob-boson-4:bit-flip-lifetime:2026-08-19]
Phase flip lifetime (phase_flip_lifetime)0.95 us at average_nb_photons=4; 0.3 us at average_nb_photons=11 microsecondsvendor claim
Vendor claim
- Method
- operating-point dependent (bit-flip protection trades against phase-flip rate)
- Citation key
[alice-bob/alice-bob-boson-4:phase-flip-lifetime:2026-08-19]
Z gate error (Z_gate_error)bit-flip contribution 5.0e-4 (4 photons) / 5.8e-8 (11 photons); phase-flip contribution 22% (4 photons) / 27% (11 photons) error probabilityvendor claim
Vendor claim
- Method
- VENDOR_UNSPECIFIED
- Citation key
[alice-bob/alice-bob-boson-4:z-gate-error:2026-08-19]
Readout (readout_SPAM_error)P0-then-MZ error: 1.7% (4 photons) / 7.6e-6 (11 photons); P+-then-MX error: 40% (4 photons) / 47% (11 photons) error probabilityvendor claim
Vendor claim
- Method
- state-preparation-and-measurement error per basis
- Citation key
[alice-bob/alice-bob-boson-4:readout-spam-error:2026-08-19]
Pricing model (availability_and_pricing_model)Available to the public since 2024-05-15 on Google Cloud Marketplace; 'Felis Cloud subscription required' to run circuits on real Boson 4 chips or emulatorsvendor claim
Vendor claim
- Source
- First cat qubit quantum chip by Alice & Bob now available on Google Cloud Marketplace - Alice & Bob · published 2024-05-15
- Method
- VENDOR_UNSPECIFIED
- Notes
- Chips hosted at Alice & Bob premises; 'first time a cat qubit has become available to the public'. Subscription pricing model exists (exact prices not recorded).
- Citation key
[alice-bob/alice-bob-boson-4:availability-and-pricing:2026-08-19]
Coherence (T1_T2_transmon_style_coherence)not publicly disclosed
Not publicly disclosed — checked 2026-08-19
- Finding
- No public disclosure found. This is a recorded, dated finding — we do not substitute an estimate or borrow a figure from a sibling device.
- Sources queried
- felis.alice-bob.com Boson 4 chips reference page, alice-bob.com Boson 4 product page
- Notes
- Cat qubits are specified by bit-flip/phase-flip lifetimes rather than conventional T1/T2; vendor publishes only the former.
QPU137 is independent and is not affiliated with, endorsed by, or sponsored by Alice & Bob. Figures above are public disclosures recorded with their sources on 2026-08-19; vendor claims are labeled as such and may not be directly comparable across measurement methods — see methodology.