The MRFM community was thrilled today (July 15, 2004) to read in Nature magazine of IBM's breakthrough experiment in single-spin imaging by magnetic resonance force microscopy (MRFM).
Shown left-to-right above are authors Raffi Budfakian, lead scientist Dan Rugar, John Mamin, and Ben Chui. Their historic imaging signal from a single electron spin is shown at right.
Our congratulations to these fine scientists, and to IBM, for this remarkable achievement.
IBM has a detailed press release, the story is also available on-line from Nature News, and of course the article itself is available (by subscription) from Nature. It's also fun to enter the search phrase "MRFM" into Google News.
The above links are pretty technical, so we thought we might make the IBM folks blush by showing the following amateur picture from a "single-spin" party at Dan Rugar's house. Present are two senior folks who helped Dan start it all: Nino Yannoni (top row, fourth from left), now retired from IBM, who partnered with Dan on the first MRFM experiment in 1992, and Cal Quate of Stanford, who was Dan's thesis advisor. The next time we see him, we'll ask Dan for the rest of the names!
And what do quantum techno-folks eat at this sort of party? Why, a single-spin cake, of course!
Now you know what happens when quantum scientists and engineers "get down".
At the UW, we think that the IBM experiment will eventually be regarded as the most important single milestone in our journey to this goal. After twelve years of effort, we are now three-quarters of the way there.The techniques described herein might eventually be extended to allow the imaging of biological molecules, and in fact were devised with this goal in mind. Relative to atomic force oscillators described in the literature, the oscillators in Table I are ~100 times smaller in linear dimension, and ~1000 times higher in frequency. It is therefore clear that developing a practical molecular imager would require a substantial effort by many scientists, and that there would be no absolute assurance of success. Nonetheless, present and projected medical needs might justify such an effort.Of the proteins encoded by the AIDS genome, only HIV-l protease has a known three-dimensional structure. Recently, a partial structure for HIV-l reverse transcriptase has also been obtained. The remaining proteins have so far proven refractory to x-ray crystallography. The missing structural information is a significant obstacle to the rational design of drugs and vaccines.
As a faculty member in a school of medicine, the author frequently observes the sequelae to our present lack of knowledge. This letter is offered in the hope that it may eventually contribute to better treatments for intractable disorders.
Noninductive detection of single-proton magnetic resonance, Applied Physics Letters, vol 58(24), page 2854--6 (1991).
How does spin observation physics work when many spins are observed simultaneously (for example, the proton spins within an HIV protein)? No one knows the answer to this question. Do the IBM results imply that the IBM cantilever is *itself* behaving as a quantum object? More broadly, can a person observe a quantized spin without being a quantized object themselves? There will surely be a lot of discussion of these points by the physics community in coming months.
As an engineering and medical research group, we at the UW think that quantum mechanics is true, and that the IBM cantilever is fully quantum mechanical. If this quantum engineering belief is correct, then the basic laws of quantum mechanics allow plenty of room for further improvements in MRFM sensitivity.
Maybe we can even go as far as the ultimate goal of imaging individual protons in a biomolecular environment. We should know within the next five years or so whether can be done. If this quantum bioimaging capability can be achieved, it will revolutionize structural biology as thoroughly as gene sequencing has revolutionized genomics.
The path forward is pretty clear: smaller, sharper, and colder cantilevers, and improved cantilever sensors. At the same time, our theoretical understanding of observational quantum spin physics needs revolutionary advances to match the IBM group's revolutionary experiment.
It's going to be an exciting time, everyone is optimistic, and everyone is working as hard as possible -- this is why the IBM work deserves to be called a breakthrough.
Now it is our generation's turn to try. Given that a single human cell is richer in structure than the center of our galaxy, we can hope to succeed not only in the narrow technical sense, but also in the broader sense of opening a new frontier for realizing our planet's hopes and dreams.