Superconducting qubits operate at millikelvin temperatures in dilution refrigerators, and their coherence times are limited by several well-documented mechanisms: two-level systems (TLS) — spurious quantum defects in dielectric materials and surfaces — are a primary cause of qubit relaxation and dephasing; phase errors constitute a second major decoherence pathway; ZZ interaction crosstalk introduces coherent errors that degrade gate fidelity even in the absence of environmental noise; and thermal noise introduced by classical control wiring that carries microwave pulses from room-temperature electronics into the cryostat is also a major source.

IBM's optically multiplexed quantum control interface encodes multiple digital qubit control signals onto distinct optical wavelength carriers in a wavelength-division multiplexed (WDM) optical signal transmitted through an optical waveguide into the cryostat. Inside the cryogenic environment, a photodetector array and superconducting LC bandpass cryogenic filters convert the optical signals back to analog RF qubit control signals. Optical fibers carry negligible thermal load compared to coaxial cables and introduce no microwave-frequency photon noise into the qubit environment.

Superconducting qubits encode quantum information in microwave-frequency modes (typically 4–8 GHz), while photonic systems and long-distance quantum networks operate in optical wavelength ranges (telecom wavelengths ~1550 nm). Converting quantum state information between these domains without introducing decoherence is a critical technology for scaling superconducting processors and linking them to photonic networks. IBM's superconducting interposer for optical transduction allows quantum information to be extracted from the cryogenic superconducting domain and transmitted as optical photons, which are far less susceptible to thermal and electromagnetic decoherence during transmission.

Photonic quantum computing offers a fundamentally different computational substrate where decoherence from thermal noise and material defects is largely absent at room temperature. Photons are inherently non-interacting with thermal environments at optical frequencies, and logical operations can be implemented through linear optics, heralding, and entanglement resources rather than through physical qubit-qubit coupling. The photonic platform's key advantage, as articulated in the patent literature, is that photons do not require cryogenic or ultra-high vacuum environments and existing fabrication technologies for miniaturized reliable photonic devices and communications infrastructure are available.

Anametric Inc.'s heralded photonic quantum circuitry employs heralded photon pair sources with filters to route photons to quantum circuit blocks, implementing dual-rail quantum photonic circuitry in which photon loss is detectable (heralded) rather than a silent error — a structural decoherence advantage over superconducting approaches where amplitude damping is unheralded. This makes photonic systems structurally better suited to loss-aware error correction protocols.

IBM's mitigation approach employs iterative optical pulse illumination of the quantum processor to scramble TLS configurations, measuring qubit relaxation times at different electric field frequencies to confirm elimination of strongly coupled TLS. TLS defects couple to qubits and induce decoherence; by using laser-on-demand scrambling, IBM demonstrates that optical pulses can reconfigure TLS defect states to improve qubit relaxation times, embedding photonic tools into the decoherence management workflow for superconducting processors.