Quantum computing promises to unlock extraordinary capabilities that will change our technological landscape as we know it.  

While the computers we all use today use bits (0s and 1s), quantum computing utilise qbits, which can be 0s, 1s and both in parallel. This parallelism means that quantum computers can process massive amounts of information in a fraction of the time it takes typical computers. 

To put this leap processing power into perspective, one quantum device, when given a task that would take conventional computers over 9,000 years to complete, took just 36 microseconds. 

This presents the prospect of huge breakthroughs across sectors like AI, drug discovery, finance, logistics and materials science. 

But alongside these opportunities comes a profound challenge: many of the cryptographic foundations that secure today’s digital world will not survive the quantum era.

What are the risks posed by quantum computing? 

Currently, our personal data, global financial systems, healthcare records, and government communications rely on public-key cryptography, like Rivest-Shamir-Adleman (RSA) and Elliptic Curve Cryptography (ECC).  

These encryption schemes are effective right now, because they rely on mathematical problems that our computers struggle to solve. It would take even the most powerful supercomputer thousands of years to crack your private key. 

But with quantum computing, these encryption schemes could be broken in a matter of hours or minutes, which would send shockwaves across the globe. 

What impact would the quantum threat have?

According to one Citi Institute report, a single-day quantum attack on just one of the major U.S. banks could cost the economy over $3 trillion in GDP and trigger major financial failures, including a six-month recession.  

However, as the report states, “the true economic cost could ultimately reflect the value of every digital interaction or asset that relies on classical cryptography, making the potential impact far larger than any previous cybersecurity risk.” 

Beyond traditional financial systems, post-quantum threats have also caught the attention of the blockchain and cryptocurrency world with University of Cambridge researchers finding that 24 of the top 26 blockchains are built purely on quantum-vulnerable signature schemes, exposing over $500 billion in Bitcoin alone. 

But the threat is effectively already here, due to harvest now, decrypt later (HNDL) strategies currently employed by cybercriminals. Adversaries are stealing encrypted data today, storing it, and simply waiting for quantum computing capabilities to decrypt and utilise it later. 

Then there’s the implications for healthcare, defence or critical infrastructure: medical and genomic records exposed, national security intelligence accessible to adversaries and electricity grids or water supplies vulnerable to attack. 

For a long time, the threats posed by quantum computers have felt too far away to demand serious, strategic attention. But this is changing fast. 

The countdown to Q-Day

The point at which quantum computers can break current encryption schemes is dubbed Q-Day by cryptographers. It was previously estimated that there’s a 19-34% chance we will reach Q-Day by 2034, rising to 60-82% by 2044. 

However, big names like Google and Cloudflare have recently announced that they are bringing their internal quantum readiness roadmaps forward to 2029.

This acceleration is due to ongoing research indicating that quantum machines could break current encryption models with significantly fewer resources than previously assumed, which sent shockwaves through the cybersecurity world.

Google issued recommendations to improve security and stability, most notably encouraging organisations to ramp up post-quantum cryptography (PQC) efforts and timelines to protect data and operations.

Post-quantum cryptography and its computational tax 

Fortunately, there is a solution to the looming threat of HNDL strategies and the arrival of Q-Day: Post-Quantum Cryptography (PQC). PQC can run on conventional hardware and networks, making it the most practical near-term defence. 

One form this takes is Fully Homomorphic Encryption (FHE), which enables processing of and computations on encrypted data, meaning it never has to be exposed, even when it’s being used. Lattice-based FHE schemes are post-quantum secure, but incredibly resource intensive. 

Many post-quantum cryptography algorithms: 

• Require larger keys and signatures 

• Involve more complex mathematical operations 

• Demand significantly higher computational overhead 

This increased computational cost impacts performance, latency, power consumption, economic efficiency and scalability when run on traditional, electronic-based systems. 

So, organisations face compromising performance for security, or security for performance. In the world of modern finance and tech that is a that trade-off no one is willing to make. 

Why post-quantum cryptography needs photonics 

Stronger cryptography will only be effective against HNDL and post-quantum threats if it is usable at a global scale. 

This is where silicon photonics, which uses light rather than electricity to move and process data, becomes a security imperative. 

Photonics (or optical computing) is uniquely suited to accelerating the underlying mathematical structures of lattice-based cryptography. Photons generate negligible heat, experience no electrical resistance, and support extremely high levels of parallelism.  

These properties make photonic systems particularly effective for compute-heavy bandwidth-intensive workloads. 

By reducing power consumption and thermal constraints, photonic compute platforms can perform complex cryptographic operations at a fraction of the energy costs and latency of conventional hardware. 

At Optalysys, we are building optical accelerators that process the Number Theoretic Transforms (NTT) at speeds and energy efficiency levels that traditional electronics cannot match.

Our fundamentally different approach merges data movement and computation, rather than treating them as separate steps.

By using photonics to apply computational operations while data is in transit, we can greatly reduce the performance tax that comes with PQC. 

Photonics is emerging as the foundational technology for future-proof security, one that aligns cryptographic strength with performance and sustainability. 

Security without compromise 

This approach allows businesses to adopt the highest standards of security – including Fully Homomorphic Encryption – without destroying their user experience or massively inflating their budget. 

We believe that vital security in the quantum age shouldn’t come with trade-offs. The time for observation has passed: 2026 will be a pivotal year for firms to take action and build their quantum resilience strategies. 

By harnessing the speed of light, we can future-proof our digital infrastructure against the quantum threat, ensuring that when the clock strikes Q-Day, the world keeps turning. 

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At Optalysys we’re pioneering the architectural revolution enabling photonic compute-in-transit. Get in touch with us to find out how we can bring efficiency gains to your use case →