The two companies say they successfully protected  live data running between New York and London at an 800 gigabit Ethernet service rate using Ciena’s WaveLogic 6 Extreme encryption solution.

The significance of the speed benchmark lies in context. Most deployed long-haul and subsea systems today operate at 100GbE or 400GbE, making 800GbE still an early-adoption proposition.

The trial demonstrated that post-quantum cryptography can be delivered at that rate across the full 6,900km span of Colt’s subsea and terrestrial network, fast enough, the companies say, to move data centre-scale volumes across the Atlantic in seconds while keeping them protected against quantum threats.

The urgency behind the trial reflects a threat that organisations are being advised to treat as present rather than future. “Harvest now, decrypt later” attacks, in which adversaries intercept and store encrypted data in transit today, intending to break it once quantum computing matures, are already considered an active risk.

According to research cited in the announcement, 69% of organisations believe quantum computing poses a real risk to current encryption methods, while 46% believe large portions of their data could be compromised. That capability could arrive as early as 2030.

Ciena’s WL6e solution uses ML-KEM, a module-lattice-based key encapsulation mechanism that is among the first post-quantum cryptography methods to be formally standardised and approved by the US National Institute of Standards and Technology as FIPS 203.

The compliance with NIST standards is commercially significant, giving enterprises and regulated industries a recognised benchmark against which to assess the solution’s viability.

Buddy Bayer, chief operating officer at Colt, framed the result in terms of infrastructure readiness rather than laboratory achievement: “This trial marks a significant step forward in protecting the world’s data as it moves across continents. It proves that quantum-safe protection can be delivered at real-world scale.”

Dino DiPerna, senior vice president of global research and development at Ciena, added that the trial demonstrates how post-quantum cryptography and high-performance optical encryption “can play an important role in protecting high-speed services over real-world long-haul and submarine networks.”

Following the trial, Colt says it can now offer quantum-safe services across a range of models, including post-quantum cryptography, quantum key distribution, symmetric key infrastructure, and hybrid approaches, across both terrestrial and subsea networks. The target customer base spans enterprises, hyperscalers, neoscalers, financial institutions, healthcare providers, and government and defence organisations.

The New York-London trial is the latest in a series of quantum-safe milestones the two companies have reached together. It follows the completion of the world’s first 1.2 terabit per second wavelength transmission across the Atlantic, announced by Colt and Ciena in November 2024, and a 2025 announcement covering the rollout of a terabit network supporting two hyperscaler customers.

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