Tag Archives: Kurt Kleiner

A demonstration of quantum surrealism

The Canadian Institute for Advanced Research (CIFAR) has announced some intriguing new research results. A Feb. 19, 2016 news item on ScienceDaily gets the ball rolling,

New research demonstrates that particles at the quantum level can in fact be seen as behaving something like billiard balls rolling along a table, and not merely as the probabilistic smears that the standard interpretation of quantum mechanics suggests. But there’s a catch — the tracks the particles follow do not always behave as one would expect from “realistic” trajectories, but often in a fashion that has been termed “surrealistic.”

A Feb. 19, 2016 CIFAR news release by Kurt Kleiner, which originated the news item, offers the kind of explanation that allows an amateur such as myself to understand the principles (while I’m reading it), thank you Kurt Kleiner,

In a new version of an old experiment, CIFAR Senior Fellow Aephraim Steinberg (University of Toronto) and colleagues tracked the trajectories of photons as the particles traced a path through one of two slits and onto a screen. But the researchers went further, and observed the “nonlocal” influence of another photon that the first photon had been entangled with.

The results counter a long-standing criticism of an interpretation of quantum mechanics called the De Broglie-Bohm theory. Detractors of this interpretation had faulted it for failing to explain the behaviour of entangled photons realistically. For Steinberg, the results are important because they give us a way of visualizing quantum mechanics that’s just as valid as the standard interpretation, and perhaps more intuitive.

“I’m less interested in focusing on the philosophical question of what’s ‘really’ out there. I think the fruitful question is more down to earth. Rather than thinking about different metaphysical interpretations, I would phrase it in terms of having different pictures. Different pictures can be useful. They can help shape better intuitions.”

At stake is what is “really” happening at the quantum level. The uncertainty principle tells us that we can never know both a particle’s position and momentum with complete certainty. And when we do interact with a quantum system, for instance by measuring it, we disturb the system. So if we fire a photon at a screen and want to know where it will hit, we’ll never know for sure exactly where it will hit or what path it will take to get there.

The standard interpretation of quantum mechanics holds that this uncertainty means that there is no “real” trajectory between the light source and the screen. The best we can do is to calculate a “wave function” that shows the odds of the photon being in any one place at any time, but won’t tell us where it is until we make a measurement.

Yet another interpretation, called the De Broglie-Bohm theory, says that the photons do have real trajectories that are guided by a “pilot wave” that accompanies the particle. The wave is still probabilistic, but the particle takes a real trajectory from source to target. It doesn’t simply “collapse” into a particular location once it’s measured.

In 2011 Steinberg and his colleagues showed that they could follow trajectories for photons by subjecting many identical particles to measurements so weak that the particles were barely disturbed, and then averaging out the information. This method showed trajectories that looked similar to classical ones — say, those of balls flying through the air.

But critics had pointed out a problem with this viewpoint. Quantum mechanics also tells us that two particles can be entangled, so that a measurement of one particle affects the other. The critics complained that in some cases, a measurement of one particle would lead to an incorrect prediction of the trajectory of the entangled particle. They coined the term “surreal trajectories” to describe them.

In the most recent experiment, Steinberg and colleagues showed that the surrealism was a consequence of non-locality — the fact that the particles were able to influence one another instantaneously at a distance. In fact, the “incorrect” predictions of trajectories by the entangled photon were actually a consequence of where in their course the entangled particles were measured. Considering both particles together, the measurements made sense and were consistent with real trajectories.

Steinberg points out that both the standard interpretation of quantum mechanics and the De Broglie-Bohm interpretation are consistent with experimental evidence, and are mathematically equivalent. But it is helpful in some circumstances to visualize real trajectories, rather than wave function collapses, he says.

An image illustrating the work has been provided,

On the left, a still image from an animation of reconstructed trajectories for photons going through a double-slit. A second photon “measures” which slit each photon traversed, so no interference results on the screen. The image on the right shows the polarisation of this second, “probe." Credit: Dylan Mahler Courtesy: CIFAR

On the left, a still image from an animation of reconstructed trajectories for photons going through a double-slit. A second photon “measures” which slit each photon traversed, so no interference results on the screen. The image on the right shows the polarisation of this second, “probe.” Credit: Dylan Mahler Courtesy: CIFAR

Here’s a link to and a citation for the paper,

Experimental nonlocal and surreal Bohmian trajectories by Dylan H. Mahler, Lee Rozema, Kent Fisher, Lydia Vermeyden, Kevin J. Resch, Howard M. Wiseman, and Aephraim Steinberg. Science Advances  19 Feb 2016: Vol. 2, no. 2, e1501466 DOI: 10.1126/science.1501466

This article appears to be open access.

University of Toronto’s (Canada) smiley face tattoo/sensor

Researchers at the University of Toronto have created a medical sensor that can be applied to the skin like a temporary tattoo.

University of Toronto Scarborough student Vinci Hung helped create the smiley face sensor shown here in the box at upper right (photo by Ken Jones)

The Dec. 3, 2012 news item on ScienceDaily notes,

A medical sensor that attaches to the skin like a temporary tattoo could make it easier for doctors to detect metabolic problems in patients and for coaches to fine-tune athletes’ training routines. And the entire sensor comes in a thin, flexible package shaped like a smiley face.

“We wanted a design that could conceal the electrodes,” says Vinci Hung, a PhD candidate in the Department of Physical & Environmental Sciences at UTSC [University of Toronto Scarborough], who helped create the new sensor. “We also wanted to showcase the variety of designs that can be accomplished with this fabrication technique.”

The Dec. 3, 2012 University of Toronto news release by Kurt Kleiner, which originated the news item, provides details about how the sensor/tattoo is fabricated and how it functions on the skin,

The new tattoo-based solid-contact ion-selective electrode (ISE) is made using standard screen printing techniques and commercially available transfer tattoo paper, the same kind of paper that usually carries tattoos of Spiderman or Disney princesses. In the case of the smiley face sensor, the “eyes” function as the working and reference electrodes, and the “ears” are contacts to which a measurement device can connect.

The sensor Hung helped make can detect changes in the skin’s pH levels in response to metabolic stress from exertion. Similar devices, called ion-selective electrodes (ISEs), are already used by medical researchers and athletic trainers. They can give clues to underlying metabolic diseases such as Addison’s disease, or simply signal whether an athlete is fatigued or dehydrated during training. The devices are also useful in the cosmetics industry for monitoring skin secretions.

But existing devices can be bulky, or hard to keep adhered to sweating skin. The new tattoo-based sensor stayed in place during tests, and continued to work even when the people wearing them were exercising and sweating extensively. The tattoos were applied in a similar way to regular transfer tattoos, right down to using a paper towel soaked in warm water to remove the base paper.

To make the sensors, Hung and her colleagues used a standard screen printer to lay down consecutive layers of silver, carbon fibre-modified carbon and insulator inks, followed by electropolymerization of aniline to complete the sensing surface.

By using different sensing materials, the tattoos can also be modified to detect other components of sweat, such as sodium, potassium or magnesium, all of which are of potential interest to researchers in medicine and cosmetology.

You can find the reserchers’ article in the Royal Society’s Analyst journal,

Tattoo-based potentiometric ion-selective sensors for epidermal pH monitoring
Amay J. Bandodkar ,  Vinci W. S. Hung ,  Wenzhao Jia ,  Gabriela Valdés-Ramírez ,  Joshua R. Windmiller ,  Alexandra G. Martinez ,  Julian Ramírez ,  Garrett Chan ,  Kagan Kerman and Joseph Wang in Analyst, 2013,138, 123-128 DOI: 10.1039/C2AN36422K

The article is open access but you do need to register for a free account with the Royal Society’s RSC [ublishing platform.

Vampire batteries in Germany too?

I posted a very brief item (April 3, 2009) about some research being done at the University of British Columbia (UBC in Vancouver, Canada) on potential medical devices called ‘vampire batteries’, which use blood as fuel. The UBC team is not alone in its pursuit. A July 15, 2011 news item, Electricity from blood sugar, on Nanowerk, highlights similar research in Germany,

Implants that obtain their energy from blood sugar and oxygen: Dr. Sven Kerzenmacher at the Department of Microsystems Engineering (IMTEK) of the University of Freiburg is researching the development of biological fuel cells with the goal of finding an inexhaustible source of power in the human body. He has been awarded the 2011 FAM Research Prize for his dissertation by the Forum for Applied Microsystems Technology (FAM). …

Researchers have yet to find an optimal method for supplying implantable medical microsystems with electrical energy. The batteries of a pacemaker, for instance, need to be replaced after roughly eight years—meaning a strenuous and expensive surgical intervention for the patient. An alternative approach is to use rechargeable batteries. However, the necessity of recharging the batteries greatly reduces the patient’s quality of life. The idea behind Sven Kerzenmacher’s research, on the other hand, is the possibility of using implantable glucose fuel cells on the basis of noble metal catalysts like platinum. Such catalysts are particularly well suited for use in implant systems due to their long-term stability and the fact that they can be sterilized. In the future, systems equipped with these fuel cells could be supplied with power by way of a continuous electrochemical reaction between glucose and oxygen from the tissue fluid.

Here’s what the team at UBC was doing (from the April 1, 2009 New Scientist article by Kurt Kleiner,),

A team at the University of British Columbia in Vancouver, Canada, has created tiny microbial fuel cells by encapsulating yeast cells in a flexible capsule. They went on to show the fuel cells can generate power from a drop of human blood plasma.

There is no mention of clinical trials, human or otherwise in the news item about the work in Germany or at UBC, which makes it difficult to guess how close they are to using these fuel cells in patients but I imagine there are still several years of lab work ahead given this comment from Kleiner’s 2009 article about the UBC team’s work. A colleague at Cornell noted,

The work is a step in the right direction, but huge challenges remain, says Lars Angenent, who works on microbial fuel cells at Cornell University.

For instance, to keep the yeast cells healthy, their waste products will need to be removed without allowing any harmful substances to leach out into the blood stream.