When you look closely enough at the physical world, things start to get fuzzy. At the quantum scale, even the simple act of measuring light involves a certain amount of noise. This isn't because of cheap sensors or a noisy room; it’s baked into the fundamental laws of physics.

Physicists call this quantum noise, and it acts as a fundamental limit on how precisely light can be measured or manipulated. For most everyday tech, the noise is too small to notice or worry about. But for quantum technologies, it can be a major roadblock.

Counteracting Quantum Noise

To get around this, researchers use "squeezed" light, a quantum state where the universe's natural static is intentionally pushed into a property we don't care about, leaving the one we do care about crystal clear. Think of it as a trade-off: quantum mechanics says you can’t know everything at once, but you can choose which part you want to know better. While normal light has balanced noise, squeezed light shifts that noise around—lowering it where it matters most for a specific task, even if that means making it noisier in a direction we don't care about.

Shaping the Nature of Light

Should we care about this seemingly invisible quirk of physics? Yes. Why? Because it's a fundamental part of today's cutting-edge tech. Gravitational-wave observatories already use squeezed light to boost their sensitivity to the faintest ripples in spacetime, which means they can now detect cosmic collisions from much deeper in space, essentially turning rare, once-in-a-lifetime discoveries into a routine weekly event. It’s also the essential foundation for continuous-variable optical quantum computing, a method that performs calculations by measuring the fluid properties of light waves, rather than just toggling individual bits on and off. By using the shape of the wave itself to carry data, researchers can tap into the massive bandwidth of light, but they need that squeezed stability to ensure the measurements stay accurate and don't drift into noise.

Recently, a team from NTT, working with the University of Tokyo, RIKEN, OptQC, and JST, hit a new milestone in making this form of light. They managed to achieve 10 decibels (dB) of squeezing in a compact optical waveguide device, a new world record for this kind of hardware. Decibels are used for this measurement because they track noise reduction on a logarithmic scale, with 10 dB representing the crucial ten-fold drop in static required for quantum computers to reliably fix their own errors.

To understand why 10 dB is a big deal, you have to look at how the light is made. Usually, researchers fire a strong "pump" laser through a special nonlinear material. The atoms in that material interact with the laser, essentially reshaping the light into its quantum squeezed state.

From Laser to Quantum

For this experiment, the research partners used a device based on periodically poled lithium niobate (PPLN), a material you’ll actually find in standard fiber-optic tech. By flipping the crystal’s electrical structure back and forth in a precise pattern, they created an environment strong enough to turn ordinary laser light into its high-performance quantum cousin.

This specific setup has a huge perk: it can handle an incredibly wide range of frequencies. While other systems are restricted to narrow bands, the waveguide-based device used in the experiment reaches into the terahertz range. That wide bandwidth means the squeezed light can support lightning-fast quantum operations, making it ideal for the massive quantum computers of the future.

Two Party Poopers

Of course, getting to these high squeezing levels is easier said than done. Two main villains usually spoil the fun: optical loss and phase error. If you lose even a few photons, the fragile quantum state falls apart. If your timing (the phase) drifts even a tiny bit, the whole thing gets out of sync.

The research team tackled both head-on:

These tweaks paid off and the experiment clocked in at 10.1 dB of squeezing, breaking the previous record. More importantly, it pushed past the threshold needed to start working on quantum error correction—the "holy grail" of making quantum computers reliable.

Since quantum computers are notoriously sensitive, any big machine will need built-in error correction to function. Higher squeezing levels make those error-correction techniques actually practical rather than just theoretical.

The vision here goes way beyond a single lab experiment; many experts see light-based quantum computers as the best path to building truly massive systems. Light travels easily through fiber optics, plays well with existing chips, and runs at incredible speeds.

Light Technology? NTT? Step Right This Way...

For NTT, this is a natural fit: the company has spent decades perfecting optical networks. By leaning into that expertise, they aren't just building a quantum computer; they’re building one that fits right into the world’s existing communications infrastructure.

Looking forward, the team wants to scale this up fast. They’re aiming for systems with tens of thousands of modes and, eventually, optical quantum computers with over a million qubits running at gigahertz speeds. For NTT, the University of Tokyo, RIKEN, OptQC, and JST, it's a major win that brings the reality of large-scale photonic quantum computing one big step closer.

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Daniel O'Connor

Daniel O'Connor joined the NTT Group in 1999 when he began work as the Public Relations Manager of NTT Europe. While in London, he liaised with the local press, created the company's intranet site, wrote technical copy for industry magazines and managed exhibition stands from initial design to finished displays.

Later seconded to the headquarters of NTT Communications in Tokyo, he contributed to the company's first-ever winning of global telecoms awards and the digitalisation of internal company information exchange.

Since 2015 Daniel has created content for the Group's Global Leadership Institute, the One NTT Network and is currently working with NTT R&D teams to grow public understanding of the cutting-edge research undertaken by the NTT Group.