# Quantum Mechanical Con Game

##### May 05, 2008

For the first time, physicists have come up with a scheme that would allow a quantum mechanical expert to win every time in a con game with a victim who only knows about classical physics. Prior quantum cons have typically been vulnerable to simple countermeasures.

A pair of physicists at Tel-Aviv University in Israel came up with the quantum cheat by imagining two people betting on the location of a particle hidden among a set of boxes. In the game, a quantum mechanical con artist named Alice turns away as her classical victim, Bob, is allowed to look inside one of two boxes sitting on a table to see if there is a particle inside. He then closes the box and Alice guesses whether or not Bob found anything in the box he chose. If she guesses correctly, she wins Bob's money, if not, she pays him.

Classically, there is a 50% chance of Alice getting it right. If instead she's adept at quantum mechanics, and has a third box hidden away, she can ensure that she always knows what Bob found in his box. All she has to do is prepare the particle in a state that essentially places it in all three boxes simultaneously, through a phenomenon known as quantum superposition. In effect, there is an equal chance of the particle turning up in any one of the boxes.

After Bob looks in one of the two boxes on the table, Alice measures the state of the particle in her hidden box. If she finds it empty, she knows Bob saw the particle in the box he opened. If she finds that the particle is in a superposition between two boxes, she knows that Bob opened the third box but didn't see anything inside. In either case, she always knows what Bob found, even though she has no way of knowing in advance where the particle will turn up or which box Bob chose to look in.

The authors of the paper admit that the current state of technology isn't good enough for a con artist to make money with quantum mechanics. But they believe that this is the first time anyone has shown that it's theoretically possible for someone like Alice to use quantum mechanics to win every time in a game that classical physics would only give her a fifty-fifty chance of winning. With advances in quantum technology, it may someday turn out that gambling is only risky for those of us who don't understand quantum mechanics.

Citation: N. Aharon and L. Vaidman, Physical Review A (forthcoming)

Source: American Physical Society

## Related Stories

#### United States, China team explore energy harvesting

4 hours ago

Six authors have described their work in harvesting energy in a paper titled "Ultrathin, Rollable, Paper-Based Triboelectric Nanogenerator for Acoustic Energy Harvesting and Self-Powered Sound Recording." ...

#### China's struggle for water security

6 hours ago

Way back in 1999, before he became China's prime minister, Wen Jiabao warned that water scarcity posed one of the greatest threats to the "survival of the nation".

#### Canada revises upward CO2 emission data since 1990

6 hours ago

Canada revised its greenhouse gas emission data from 1990 to 2013 in a report Friday, showing it had higher carbon dioxide discharges each year, and a doubling of emissions from its oil sands.

#### Samsung removes logo on smartphones in Japan

6 hours ago

Samsung has removed its corporate logo from its new smartphones sold in Japan, a company spokeswoman confirmed Saturday.

#### New Google security chief looks for balance with privacy

6 hours ago

Google has a new sheriff keeping watch over the wilds of the Internet.

#### Fish found in suspected tsunami debris boat quarantined

16 hours ago

The wreckage of a fishing boat that appears to be debris from the 2011 Japanese tsunami was carrying some unexpected passengers—fish from Japanese waters—when it was spotted off the Oregon coast.

## Recommended for you

#### Heat makes electrons spin in magnetic superconductors

15 hours ago

Physicists have shown how heat can be exploited for controlling magnetic properties of matter. The finding helps in the development of more efficient mass memories. The result was published yesterday in Physical Review Le ...

#### Portable MRI could aid wounded soldiers and children in the third world

Apr 23, 2015

Scientists at Los Alamos National Laboratory are developing an ultra-low-field Magnetic Resonance Imaging (MRI) system that could be low-power and lightweight enough for forward deployment on the battlefield ...

#### Examining Einstein—precise experiments using lasers in space

Apr 23, 2015

Tests carried out in zero-gravity on board the FOKUS research rocket. Successful demonstration of technology for the QUANTUS mission.

#### ICARUS neutrino experiment to move to Fermilab

Apr 23, 2015

A group of scientists led by Nobel laureate Carlo Rubbia will transport the world's largest liquid-argon neutrino detector across the Atlantic Ocean from CERN to its new home at the US Department of Energy's ...

#### National security on the move with high energy physics

Apr 23, 2015

Scientists are developing a portable technology that will safely and quickly detect nuclear material hidden within large objects such as shipping cargo containers or sealed waste drums. The researchers, led ...

#### Mechanical cloaks of invisibility—without complicated mathematics

Apr 23, 2015

A honeycomb is a very stable structure. If it has a larger hole, however, stability is largely lost. What might a honeycomb look like, which survives external forces in spite of a hole? Such stable types ...