Most of us don't really consider what it costs to remember something.

Whether your phone saves a photo, your laptop opens a document, or a server updates a database, the whole process feels weightless, almost free. But every one of those tiny actions leaves a physical footprint. Energy is consumed, heat is released, and something in the physical world fundamentally changes.

Everything Has A Price

We’ve known this, in theory at least, for a long time. There’s a principle in physics which says that erasing information always carries a minimum energy price tag. Even something as basic as resetting a memory cell—flipping a 1 back to a 0—inevitably produces a tiny burst of heat. For years, the working assumption has been that if you just perform that reset slowly enough, you could get very close to that theoretical minimum.

The tricky part is that most of this has stayed buried in math or high-end lab experiments that don’t look anything like the gadgets we actually use. Real-world devices are noisy, signals are faint, and the effects we’re trying to measure are even fainter. For a long while, it’s been hard to say with any certainty if everyday memory chips actually behave the way the textbooks say they should.

Detecting Minute Energy Changes

This is where NTT’s recent work could be interesting. Company researchers have built a silicon nano-device that can detect changes at the level of a single electron, letting researchers directly observe the microscopic heat signatures and shifts in entropy (basically a measure of disorder) that happen the moment a memory is reset.

NTT applied the device to a structure based on a DRAM (Dynamic Random Access Memory) cell—the basic unit of memory in DRAM, used to store a single bit of data and the exact kind of memory found in almost every modern computer. By tracking how individual electrons move through the system, they were able to calculate the heat generated and the change in entropy during the initialization phase, which is when stored data is cleared out.

The findings are a bit… Okay, they’re a bit unexpected. Even when NTT researchers ran the operation incredibly slowly, the device never hit that theoretical floor for energy cost. There was always a lingering amount of heat produced, more than the ideal physics case would predict.

It might seem like a minor technicality, but it changes the whole conversation. It suggests that real devices operating in the real world have limits that theory alone doesn't quite catch. The simple idea that we can reduce energy use indefinitely just by slowing things down doesn't appear to hold up in practice.

Knowing Where Energy Is Lost

At the same time, NTT’s work fills a major gap. It gives us a way to see, in high definition, where energy is being used or lost inside a device. It’s not just about total power consumption anymore; it’s about knowing when and where energy loss occurs.

That kind of visibility could be vital. As computing scales up and energy efficiency becomes a global priority, these tiny effects start to matter a lot. If you can finally measure them, you can start designing around them.

It also opens the door to some wilder possibilities. Think about it: the same laws of thermodynamics that limit efficiency might actually start to be used as a resource. We might eventually be able to take the noise and fluctuations we usually ignore and bake them into entirely new types of computing.

For now, we’re left with a much clearer picture of something we’ve long suspected but rarely seen. Information might feel like it exists in the ether, but it’s always tethered to the physical world. Even when a system decides to forget something, it still has to pay the bill.

Innovating a Sustainable Future for People and Planet

For further information, please see this link:
https://group.ntt/jp/newsrelease/2026/04/23/260423a.html (Japanese)

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NTT Basic Research Laboratories
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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.