Quantum Memory: The Device That Breaks Bitcoin and Replaces It

Oxford quantum‑computing lecturer Stefano Gogioso argues that the development of portable, long‑term quantum memory will be a pivotal milestone for both cryptography and digital assets. He claims the same hardware needed for fault‑tolerant quantum computers – which could threaten Bitcoin’s signatures – would also enable a new form of "quantum money".

Why Quantum Memory Matters

Quantum memory would store quantum states for extended periods, potentially months or longer, unlike current laboratory systems that preserve states for only seconds. Gogioso outlines three practical requirements for a usable device:

• Stability measured in months or indefinitely.
• Portability, initially in a crate and eventually in a pocket‑sized form.
• Capacity to hold billions of distinct quantum states.

From Fault‑Tolerant Computing to Quantum Money

Fault‑tolerant quantum computers must keep fragile states alive against noise for the duration of a calculation. Removing the computing element leaves a quantum memory device, which Gogioso says is an unavoidable component of any roadmap toward large‑scale quantum machines. He also notes that a single‑use, sealed cartridge filled with quantum states could satisfy many applications without needing decades‑long stability.

Implications for Bitcoin

A March study involving Google Quantum AI, the Ethereum Foundation, and Stanford estimated that breaking Bitcoin’s elliptic‑curve signatures would require fewer than 500,000 physical qubits, a figure that assumes fault tolerance – essentially quantum memory. Consequently, the same technology that could compromise Bitcoin could also power quantum money, meaning investment in fault‑tolerant hardware supports both outcomes.

Security Model Shift

Quantum money relies on entangled pairs that carry no usable information until measured. If a shipment of such quantum states were intercepted, the attacker would obtain only inert material, not a usable key. This reverses the traditional risk model where stolen classical keys are immediately exploitable.

Timeline Outlook

Industry forecasts place quantum‑computing breakthroughs around 2028‑2029, with regulatory bodies setting quantum‑readiness deadlines for banks by 2030 and planning to retire current elliptic‑curve signatures by 2035. Gogioso does not provide a specific release date for quantum money, emphasizing the inevitability of the resource rather than a near‑term product.

Open Questions

Key challenges remain, including how to issue and manage quantum‑memory‑based assets without a custodian and how to handle loss or decay of the quantum states, which would render the associated value unrecoverable.