Colt Technology Services and Ciena say they have completed a successful transatlantic test of a quantum-safe data link, pushing traffic between New York and London at 800 Gbps across 6,900 km of Colt’s land and subsea network. The point is not just speed bragging rights; it is an attempt to show that post-quantum cryptography can ride on top of modern optical infrastructure without slowing the pipe to a crawl.
The timing makes sense. Telecom operators, cloud providers, and data-center networks are starting to prepare for a future where today’s encryption could eventually be vulnerable to quantum computing, while attackers can already archive encrypted traffic now and try to decrypt it later. That ”harvest now, decrypt later” threat has become a useful sales pitch for post-quantum cryptography, but the engineering challenge is harder: security has to scale without kneecapping throughput, especially for AI traffic moving between data centers.
How the Colt-Ciena test was set up
Ciena’s WaveLogic 6 Extreme platform handled the transmission, with post-quantum cryptography aligned to NIST standards and integrated with 1.6 Tbps coherent optical technology. Colt says the test shows that quantum-resistant protection can be added on one of the world’s busiest communications paths without sacrificing the kind of speed enterprise and hyperscale customers now expect.
- Speed tested: 800 Gbps
- Route: New York to London
- Distance: 6,900 km
- Platform: Ciena WaveLogic 6 Extreme
- Security: post-quantum cryptography compliant with NIST standards
Colt’s broader security push
This was not a one-off science project. Colt has already been pushing a mix of post-quantum cryptography, quantum key distribution, symmetric key infrastructure and hybrid security architectures across its terrestrial and subsea network. That broader menu matters because different customers will want different levels of protection, and the industry still has to decide how much quantum-ready security is enough before the threat becomes less theoretical and more expensive.
There is also a commercial subplot here. In 2024, the companies said they had delivered the industry’s first transatlantic signal at 1.2 Tbps, and in 2025 they unveiled a new terabit-scale network for hyperscalers. The latest test shifts the focus from simple capacity gains to security, which is probably where the real spending pressure will come from next.
What happens next for transatlantic optics
The obvious question is whether other carriers can match this combination of speed and quantum-safe protection quickly enough to matter. If AI workloads keep driving more east-west traffic between major cloud hubs, transatlantic networks will need to do two things at once: get faster and get harder to break. That is a tougher sell than pure bandwidth, but it is also where the next round of competitive differentiation is headed.