'Quantum criticality': Ultracold experiments heat up quantum research

Enlarge

This false color image shows the average density of cesium atoms taken during multiple experimental cycles for studying quantum criticality in the ultracold laboratory of Cheng Chin, associate professor in physics at UChicago. The density is lowest in the white area on the outside, highest toward the center, where higher numbers of atoms are blocking the incoming infrared laser light. Xibo Zhang collected these data in connection with his recently completed doctoral research at UChicago. (Xibo Zhang and Cheng Chin)

(PhysOrg.com) -- University of Chicago physicists have experimentally demonstrated for the first time that atoms chilled to temperatures near absolute zero may behave like seemingly unrelated natural systems of vastly different scales, offering potential insights into links between the atomic realm and deep questions of cosmology.

This ultracold state, called “quantum criticality,” hints at similarities between such diverse phenomena as the gravitational dynamics of black holes or the exotic conditions that prevailed at the birth of the universe, said Cheng Chin, associate professor in physics at UChicago. The results could even point to ways of simulating cosmological phenomena of the early universe by studying systems of atoms in states of quantum criticality.

“Quantum criticality is the entry point for us to make connections between our observations and other systems in nature,” said Chin, whose team is the first to observe quantum criticality in ultracold atoms in optical lattices, a regular array of cells formed by multiple laser beams that capture and localize individual atoms.

UChicago graduate student Xibo Zhang and two co-authors published their observations online Feb. 16 in Science Express and in the March 2 issue of Science.

Quantum criticality emerges only in the vicinity of a quantum phase transition. In the physics of everyday life, rather mundane phase transitions occur when, for example, water freezes into ice in response to a drop in temperature. The far more elusive and exotic quantum phase transitions occur only at ultracold temperatures under the influence of magnetism, pressure or other factors.

“This is a very important step in having a complete test of the theory of quantum criticality in a system that you can characterize and measure extremely well,” said Harvard University physics professor Subir Sachdev about the UChicago study.

Physicists have extensively investigated quantum criticality in crystals, superconductors and magnetic materials, especially as it pertains to the motions of electrons. “Those efforts are impeded by the fact that we can’t go in and really look at what every electron is doing and all the various properties at will,” Sachdev said.

Sachdev’s theoretical work has revealed a deep mathematical connection between how subatomic particles behave near a quantum critical point and the gravitational dynamics of black holes. A few years hence, offshoots of the Chicago experiments could provide a testing ground for such ideas, he said.

There are two types of critical points, which separate one phase from another. The Chicago paper deals with the simpler of the two types, an important milestone to tackling the more complex version, Sachdev said. “I imagine that’s going to happen in the next year or two and that’s what we’re all looking forward to now,” he said.

Other teams at UChicago and elsewhere have observed quantum criticality under completely different experimental conditions. In 2010, for example, a team led by Thomas Rosenbaum, the John T. Wilson Distinguished Service Professor in Physics at UChicago, observed quantum criticality in a sample of pure chromium when it was subjected to ultrahigh pressures.

Zhang, who will receive his doctorate this month, invested nearly two and a half years of work in the latest findings from Chin’s laboratory. Co-authoring the study with Zhang and Chin were Chen-Lung Hung, PhD’11, now a postdoctoral scientist at the California Institute of Technology, and UChicago postdoctoral scientist Shih-Kuang Tung.

In their tabletop experiments, the Chicago scientists use sets of crossed laser beams to trap and cool up to 20,000 cesium atoms in a horizontal plane contained within an eight-inch cylindrical vacuum chamber. The process transforms the atoms from a hot gas to a superfluid, an exotic form of matter that exists only at temperatures hundreds of degrees below zero.

“The whole experiment takes six to seven seconds and we can repeat the experiment again and again,” Zhang said.
The experimental apparatus includes a CCD camera sensitive enough to image the distribution of atoms in a state of quantum criticality. The CCD camera records the intensity of laser light as it enters that vacuum chamber containing thousands of specially configured ultracold atoms.

“What we record on the camera is essentially a shadow cast by the atoms,” Chin explained.

The UChicago scientists first looked for signs of quantum criticality in experiments performed at ultracold temperatures from 30 to 12 nano-Kelvin, but failed to see convincing evidence. Last year they were able to push the temperatures down to 5.8 nano-Kelvin, just billionths of a degree above absolute zero (minus 459 degrees Fahrenehit). “It turns out that you need to go below 10 nano-Kelvin in order to see this phenomenon in our system,” Chin said.

Chin’s team has been especially interested in the possibility of using ultracold atoms to simulate the evolution of the early universe. This ambition stems from the quantum simulation concept that Nobel laureate Richard Feynman proposed in 1981. Feynman maintained that if scientists understand one quantum system well enough, they might be able to use it to simulate the operations of another system that can be difficult to study directly.

For some, like Harvard’s Sachdev, quantum criticality in ultracold atoms is worthy of study as a physical system in its own right. “I want to understand it for its own beautiful quantum properties rather than viewing it as a simulation of something else,” he said.

More information: “Observation of Quantum Criticality with Ultracold Atoms in Optical Lattices,” by Xibo Zhang, Chen-Lung Hung, Shih-Kuang Tung, and Chen Chin, Science, March 2, 2012, Vol. 335, No. 6072, pp. 1070-1072, and online Feb. in Science Express Feb. 16.

Provided by University of Chicago (news : web)

Newscribe : get free news in real time 

Related posts:
IBM takes giant step to faster, quantum computers
A quantum connection between light and motion
Quantum strategy offers game-winning advantages ...
IBM Scalable Quantum Computing
Quantum Computing Thrives on Chaos
Engineering the Computer of the Future, One Atom at a ...
 

Malaysia could go bankrupt by 2019?

Why Malaysia won’t go bankrupt

TRANSFORMATION BLUES By IDRIS JALA idrisjala@pemandu.gov.my
 
The Government is not in dire financial straits right now. By all measures its finances are good, but as in any situation involving finances, this is not to say it cannot be better.

I AM frequently asked why I said Malaysia could go bankrupt by 2019. I have had many queries asking for clarification and this has become one of my transformation blues.

In charting out our transformation journey in 2009, one of the first things the Prime Minister and the cabinet did was to list our current status, say where we want to be and set up a programme for transformation to get us there.

Amongst the many things on the list was a need to rationalise subsidy and so we ran a lab to do this.

During our open day, we engaged the public on the lab recommendation on the subsidy rationalisation. I wanted to be as frank as possible and to make it clear what the consequences of inaction would be.

Perhaps I was too frank but what I said has been misrepresented on a number of occasions, and I have since been saddled and hobbled with an unnecessary problem.

Habitual critics latched on to a small part of one of my first presentations where I said we have to change our spending patterns for sustained fiscal health.

Against a backdrop of several caveats and conditions, I said that we would be bankrupt by 2019 IF we continued to increase our subsidies and borrowings the same way we did before and IF our economy grows at less than 3% annually.

I've worked in Shell for more than 20 years, a company that is famous for its scenario planning techniques.

In layman terms, scenario planning means describing a future that could either be “good, bad or ugly” and doing our best to achieve the “good scenario” and avoid the “bad and ugly”.

My statement was heavily qualified but little or no mention was made of the clear caveats that I had put forward.

I still stand by what I said and it is important that my statement is taken together with the conditions.

This statement has been taken out of context so many times that it really gave me the blues - I have been talking till I turned blue in my face explaining what I meant!

Let me say in the clearest terms that my intention then was to illustrate the consequences of inaction when faced with tough decisions. We cannot continue to subsidise the way we have.

Let me also state that the Government is not in dire financial straits right now. By all measures its finances are good, but as in any situation involving finances, this is not to say it cannot be better. Here's why.

Our debt as at end 2011 is 53.8% of gross domestic product (GDP the sum of goods and services produced in the country) and the budget deficit is better than the 5.4% target of GDP.

Compare this with Greece's debt which stands at 110% of GDP and a budget deficit of 13% and it is obvious that we are not anywhere close to a crisis.

Subsidy rationalisation

Globally, many economists are cautioning the Governments against rising national debts. In 2009 the year for which the figures I used when I talked about subsidy rationalisation we had to increase government spending via our “economic stimulus package” in the face of the world financial crisis caused by the sub-prime mortgage problem in the United States.

This had spill-over effects into 2010 as well. But the debt as a percentage of GDP has begun to level off while the budget deficit, again as a percentage of GDP, has begun to significantly decline and as our economy continues to grow. We are reversing the situation.

In a simplified system to assess whether countries are in a sovereign debt crisis, the Boston Consulting Group (BCG) uses a graphical representation to identify countries with a potential problem.

Public debt as a percentage of GDP is plotted on the vertical axis while surplus or deficit in the national budget as a % of GDP is plotted on the horizontal axis.

BCG identifies a potential problem looming if public debt is 100% or over of GDP while simultaneously the budget deficit is 10% or more of GDP (see chart).

The more a country is to the left of the chart and the higher on the vertical axis, the greater the risk of a potential debt crisis but note that a country has to be simultaneously in problem in both areas to be regarded as a big risk.

If you look at Singapore, public debt as a percentage of GDP is 100% in the problem area but only for one of the two criteria but there is hardly any budget deficit to speak of in the republic.

Nobody considers Singapore a financially troubled country.

For Malaysia, it is important to notice that it has moved to the right in 2011 compared with its position in 2009 and 2010 while there is hardly any upward movement. That indicates a move in the right direction.

Based on this analysis, we are better than the United Kingdom, the United States, Spain, Italy, Portugal and Japan, to name a few. We will get into the safe zone soon enough.

The problem I highlighted using 2009 figures, making the caveat that IF debt continued to increase at previous levels we can have a serious problem in 2019 and IF we grow less than 3% annually, does not exist anymore.

Making improvements

Why? Because we are making improvements on both counts.

Firstly, as a responsible Government, in 2010, we began the process of gradually reducing subsidies for fuel, sugar, electricity and so on, knowing fully well that this was unpopular.

Secondly, our GDP grew by 7.2% in 2010 and 5.1% in 2011 and that's an average of 6.2%; we are meeting our Economic Transformation Programme (ETP) target. Of course, we can and should do much more.

As I have pointed out in previous presentations very little of our subsidies amounting to billions of ringgit every year go to the poor, the rich get most of it. We must rationalise the subsidy system not do away with it and cut other extraneous expenditures.

However, we continue to help the poor via our GTP initiatives e.g. Azam programmes and BR1M for the low income households and rural infrastructure programmes.

On the other side of the equation, we must increase government revenue sources by introducing such measures as a goods and services tax (GST) and get more economic activity going. We can exclude necessities from the tax.

We are already succeeding. We have the ETP and we are growing our revenue we had additional tax revenue of RM26bil in 2011. This has allowed us to finance rakyat-centric programmes such as BR1M.

Why, if we continue to make progress by these measures, we may even be able to balance the budget come 2020 even though that will welcomingly surpass our own target.

I know there will be critics who will say that I have changed my mind on the bankruptcy issue. I haven't changed my position vis-a-vis scenario planning.

I always believe in describing the “good, the bad and ugly” scenarios (that hasn't changed) i.e. the “good” scenario is if we successfully implement our ETP, we will achieve high income status by 2020.
The “bad or ugly” scenario is if we don't do anything to avoid it, then we can go bankrupt.

The fact is we are doing a lot of things to transform our country. So, we will not go bankrupt.

With the implementation of the ETP, we must acknowledge that Malaysia is on the right track in transforming its economy. The average annual GDP growth in two years (2010 and 2011) is more than 6%. In 2011, we met our GNI and investment targets, trade reached a record high of RM1.27 trillion in 2011.

We cut our deficit in 2011. In April, our PM will be releasing our ETP and GTP annual reports which provide all the details of our country's achievement.

Let me conclude by quoting Dale Carnegie: “It is tragic when we put off living. We dream of a magical rose garden over the horizon and miss the roses blooming outside our windows”.

Datuk Seri Idris Jala is CEO of Pemandu and Minister in the Prime Minister's Department. Fair and reasonable comments are most welcome at idrisjala@pemandu.gov.my

Related post:
Malaysians, work hard to succeed !
Moody's declares Greece in default of debt 

Arrests at New York 'Occupy' protests

Clashes and arrests in Zuccotti Park as 'Occupy' activists mark six months since birth of anti-corporate greed movement.
Critics say the movement lacks demands and direction [GALLO/GETTY]  Police and activists have clashed at a park in New York where hundreds of people had gathered to mark six months since the beginning of the city's Occupy Wall Street protests. The clashes, late on Saturday, came as some activists attempted to re-occupy Zuccotti Park, which police had earlier declared closed for the evening. The Manhattan park, close to Wall Street, was where the anti-corporate greed protest movement began in September last year. Activists spent months camping at the site, prompting similar demonstrations in other US cities and abroad. Police began making arrests after several hundred protesters had remained there, with some erecting a makeshift tent of cardboard and tarpaulin in contravention of rules banning shelters in the park. More than 100 police officers pushed through the park, clashing with protesters who attempted to stand their ground, The Associated Press news agency reported. The Reuters news agency reported that dozens of protesters had been led away in handcuffs, although there has been no official word on the number of arrests. Earlier in the day, hundreds of protesters had marched on nearby Wall Street, resulting in another unspecified number of arrests, police said. Organisers vowed that Saturday's rally was the first of several events planned to protest against perceived economic injustice. 'We are going to take it back' One of the activists taking part in the gathering said he hoped the park would again become a home for protesters, in defiance of a police ban on sleeping there which led to the eviction of the protest camp's occupants after two months. In-depth coverage of the global movement "They're hoping we'll all go away because it's cold," said Rob, 28, declining to give his last name. "The park's become the symbol both for us and for them. We are going to take it back." Protester Paul Sylvester, 24, of Massachusetts said he was "thrilled" to be back at the park but said he hoped the movement would begin to crystallise around specific goals. "We need to be more concrete and specific," he said. Critics say the Occupy movement lacks demands and direction and has lost momentum. But warmer spring weather in the US has brought expectations that Occupy leaders will try to regain their momentum. Protesters seemed invigorated by their relatively large numbers compared to the small turnouts during street demonstrations over the winter. At the park on Saturday, street theatre troupes performed and guitar players led sing-alongs. Some protesters marched through the streets of the financial district, chanting "bankers are gangsters" and cursing at police. Liesbeth Rapp, 27, who was performing street theatre about economic injustice, said protesters were ready to make some changes. "I think we've learned a lot about being strategically and tactically smarter," she said. "We're learning to decentralise, and to work in smaller groups." Source: Agencies  Newscribe : get free news in real time