The Space Between – How is Quantum Tunneling Pushing the Limits of Magnetic Data Storage?

floppy disks

In a world of magnets and miracles, step back in time with us for a moment as we return to America of 1956. The Eisenhower Administration had just entered into what was to become the Vietnam War; it was a time of mounting political turmoil but of economic surety. Society was re-emerging from its post-war doldrums: Elvis Presley, Fats Domino, and Doris Day topped the music charts; and Peyton Place was on the New York Times best-seller list for 59 weeks. Eschewing the1940s stark simplicity, fashion saw a romantic revival with women flaunting ultra-feminine silks and chiffons while men were dashing in tweeds and Edwardian cut velvets. John Wayne, Charlton Heston, and Zsa Zsa Gabor graced our movie screens and we thrilled to the terror of the movie The Invasion of the Body Snatchers. It was a heady time indeed…

That year was destined to be a great one in computing and electronics history. Over at Bell Labs in Murray Hill, NJ, William Shockley, John Bardeen and Walter Brattain – inventors of the point-contact transistor – won the Nobel Prize for Physics ‘for their researches on semiconductors and their discovery of the transistor effect.’(1) And in the International Business Machines Corporation’s (IBM) Poughkeepsie, NY, lab, Arthur L. Samuel demonstrated the first use of artificial intelligence by programming an IBM 704 to not only play a game of checkers, but to learn from its experience. A year later, the ground-breaking programming language FORTRAN, dubbed ‘the mother tongue of scientific computing’ by Cecil E. Leith, was developed by the company for scientific and engineering applications. And also in this year, IBM established its nanotechnology research laboratory in San Jose, the beating heart of California’s nascent Silicon Valley.

“It’s amazing to know that IBM actually had 35 years of nanotechnology history before it was even a search term.”

So research on the nano-level – despite being a seemingly new kid on the technology block – actually has a longer lineage than we might imagine. As one reader noted: “It’s amazing to know that IBM actually had 35 years of nanotechnology history before it was even a search term.” Amazing indeed. And the drumbeat of technological advancement inevitably brings with it the call for increasing developments in data storage. Let’s use a stellar example …

Just thirteen years after the establishment of IBM’s San Jose laboratory, the world witnessed an unprecedented achievement. In 1969, the Apollo 11 lunar landing mission set Neil Armstrong and Buzz Aldrin on the moon’s surface, with Michael Collins piloting the command module, Columbia, in lunar orbit. The Apollo Guidance Computer (AGC) which brought the astronauts on an approximate 480,000 miles round trip across space was coded via assembler language with instructions for the voyage being fed into the AGC via punch cards. The AGC – then state-of the-art – boasted a massive 64K of memory.(2) Sixty-four kilobytes. Fast forward to almost 50 years later and our modern toasters demand more memory than that. And with costs dropping, the need for RAM and greater hard drive capacity increasing, and the impractical nature of storing information on punch cards, magnetic disk drives are now the norm. The bleeding edge of new state-of-the-art storage technology lies with the work of companies like Seagate whose research prioritizes the development of high-capacity disks on a nano-scale, manufactured in cleanroom environments. According to The Register, a global online tech publication, leaders in drive recording technology are actively reconsidering the model of data storage. Previous paradigms saw the magnetized domain of the disk platters arranged flat on the disk surface, but new methods of perpendicular magnetic recording (PMR) flip that model through 90 degrees, storing the domains vertically. This change allows for an increase in data storage capacity in the same physical area. How much? Actually, it’s quite a lot. Seagate reports that using PMR the areal density of the disk comes in at 800GBit per inch squared which is a climb from just 400GBits in the same area in their 2009 prototypes. And then there’s also their ability to leverage shingled magnetic recording (SMR), and heat-assisted magnetic recording (HAMR).

Welcome to the quantum world of single atom storage…

So with an effective doubling of capacity within eight years, how could this rate of progress be improved upon? Well, astute readers will no doubt have noticed that each of these three technologies use magnetism in their recording technology. And the use of this property is not confined to traditional disk drives. Let’s take a close look – a really close look – at a form of technology that could allow magnetic storage at densities 1000 times greater than currently hard disks allow.(3) Welcome to the quantum world of single atom storage…

When we cast our minds back to our high school days, we recall that atoms are the most basic units of matter. Composed of subatomic particles collectively called fermions, atoms contain neutrons and protons in the nucleus, and a third component – electrons – which circle in a cloud whose radius is 10,000 times greater than the nucleus.(4) And in addition to serving as building blocks of all matter, it now seems that atoms can also be building blocks of data storage. But how can we store information on a single atom? The first step is being able to actually see them on an individual basis. If atoms can be seen, we can target them and we can manipulate them. And to do that, we need an extremely powerful microscope.

Developed in 1981 by IBM scientists in Zürich, Gerd Binnig and Heinrich Rohrer, the Scanning Tunneling Microscope (STM) went on to win the Nobel Prize for Physics in 1986. A type of custom electron microscope, the STM leverages a concept of quantum mechanics – tunneling – that allows the wave-like properties of electrons to ‘tunnel’ through solid surfaces to reach regions of space within an object that are unreachable within the parameters of classic physics. Binnig and Rohrer had been investigating surface conductivity and found that an electrical voltage passed between the tip of a tungsten needle positioned a few angstroms (one tenth of a millimicron, also expressed as one ten millionth of a millimeter) from a sample allowed variations in the tunneling current to be processed into a topographical map of the object’s surface. Operating in extreme vacuum conditions to preclude contamination by air molecules or particulates, the STM shows incredible three-dimensional images – with a resolution so high that it can resolve single atoms – and uses helium, an inert, monoatomic gas, as a coolant that ‘allows the atoms to retain their magnetic orientations long enough to be written and read reliably.’(5)

…this form of data storage would allow 35 million songs – a ridiculously huge iTunes library – to be stored on a physical medium the size of a credit card.

But the microscope is only half of the equation. In order to use it to encode data on an atomic level, researchers needed to identify a substance that could be permanently transformed in order to reflect that change. And the answer lay in a rare earth element first described by Swiss chemists Marc Delafontaine and Jacques-Louis Soret in 1878. Holmium, a somewhat non-descript silver-white colored element, is a lanthanide, and is both ductile and malleable. It is also magnetic – a small fact that had traditionally made it suitable for use in creating magnets and for use as a flux concentrator for high magnetic fields. But the renewed interest in this element is due to the fact that it is also an ideal tool facilitating magnetic data storage on an atomic level. How? If we can see the individual atoms of a magnetic substance using the STM and we can access them, we can turn them into miniature code buckets. In theory, using an electrical current to fix the direction of an atom’s spin – ‘spin up’ or ‘spin down’ – each atom can become a storage container for one data bit – a zero or a one in the classic binary paradigm. By permanently fixing the spin at this individual atomic level, the data could be sequenced – in effect, stored and read. And all of this can be done on an incredibly small scale. As the article in notes, given that two magnetic atoms separated by just one nanometer (which is a millionth the width of a pinhead) can be written to and read from independently of each other, this form of data storage would allow 35 million songs – a ridiculously huge iTunes library – to be stored on a physical medium the size of a credit card.(6)

Since the very early days of the semi-conductor industry, the cleanroom has traditionally been the locus of component development and manufacture.

But apart from being able to store ever more digital data in an ever diminishing physical space, is there another benefit to this technology? We’re glad you asked. Since the very early days of the semi-conductor industry, the cleanroom has traditionally been the locus of component development and manufacture. A contamination-controlled environment is critical to the production of chips since the silicon wafers are etched and imprinted using a toxic mixture of acids and solvents with chemicals such as toluene, arsenic, benzene, and also trichloroethylene being historically integral to the process. Any particulate contamination spells disaster for the finished product. But the problem with this traditional manufacturing is that the chemical cocktail used contains suspected carcinogens (although the industry did begin phasing out the use of glycol ethers around 1995) and some have also been associated with an increased incidence of birth defects among workers exposed to them. And workers on the assembly line would have repeated contact with them in the routine performance of their tasks.

But by moving to the new form of magnetic technology and embracing atomic encoding, it might be that we can by-pass the need for use of these chemicals. By changing the requirements for manufacturing, we might be able to change the processes and create a better product with fewer health considerations. Within the U.S., guidelines from the Occupational Health and Safety Administration (OSHA) are very clear, but as an article in Mother Jones magazine points out:

“At particular risk […are] workers in developing countries, where job-safety rules are often weak and where chip factories routinely use chemicals and equipment that are no longer considered safe in the industrialized world.” (7)

Per the Mother Jones article and the San Jose Mercury News, more than fifty lawsuits brought against IBM by workers allegedly suffering from cleanroom-induced illnesses were settled, although the settlement terms of the litigation were not disclosed.(8) And due to the nature of the cases, we cannot know for sure whether exposure to chemicals such as acetone and benzene actually caused these workers’ conditions. However, given that we are now able to move to a different – potentially less dangerous – model of data storage manufacturing, it would seem prudent to accelerate the pace of change.


And then there’s also the question of 5D data recording. While the use of the STM in making possible data storage on the atomic level is exciting, another development is already waiting in the wings. Five-dimensional data storage leverages the power of glass nanostructures to encode massive amounts of information in a supremely stable environment. The one-inch diameter disks contain what researchers are calling ‘nanogratings’, which change how light is reflected. Instead of bouncing back in one of two ways (where light reflected back off a bump on a standard disk is sequenced as a ‘one’ and where there’s no bump the light is seen as a ‘zero’), 5D disks allow light to be sequenced according to “the nanograting’s orientation, the strength of light it refracts, and its location in space on the x, y, and z axes.”(9) And with this technology comes the ability to store 360 terabytes of data per one-inch glass disk for a projected lifespan of 13.8 billion years.

Now, given that this is a timespan as old as the universe and more than three times the age of our planet, THAT is a truly mind-boggling possibility and begs the question: As the ultimate legacy of our culture – our humanity – what would you like to see stored for future generations, or even for future civilizations?

Do you think that this new magnetic data storage could revolutionize the industry? Do you have data you’d like to see stored on the atomic level? Or are you waiting for 5D technology to hit the commercial shelves? As always, we’d love to know your thoughts.


  6. ibid

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