Biological and quantum computing are separate unconventional-computing branches. Quantum computers manipulate quantum states. Neural biocomputers use the dynamics and plasticity of living neural networks.
Biocomputer
Quantum computer
Information substrate
Living cells and networks
Qubits
Characteristic resource
Plasticity, recurrence and self-organisation
Superposition, interference and entanglement
Environment
Physiological culture conditions
Platform-dependent control; many systems require extreme isolation or cooling
Likely role
Adaptive or dynamical specialist computation
Algorithms with useful quantum speedups
Different workloads, different physics
The two technologies expose different physical phenomena to computation. A useful comparison therefore starts from a particular workload and the complete system-level cost.
Could they coexist?
Yes. Both are likely to operate as specialist components attached to conventional computing for the foreseeable future. A hybrid system could use ordinary processors for orchestration while calling specialised substrates only where they offer measurable value.