An
international collaboration and a newly published paper may have just settled a
century old physics debate.
Quantum
mechanics is spooky. Entanglement – a component of quantum mechanics – tells us
that two particles can be directly connected even across vast distances. If you
measure the spin of one particle, you immediately know the spin of its
counterpart.
mechanics is spooky. Entanglement – a component of quantum mechanics – tells us
that two particles can be directly connected even across vast distances. If you
measure the spin of one particle, you immediately know the spin of its
counterpart.
Physicists
have labeled this behavior as “spooky” as it doesn’t follow everyday logic.
Common sense tells us that objects across the universe cannot possibly be
connected, yet in the quantum realm, they are. Quantum mechanics also says that
properties of particles are only fixed when the particle is observed.
have labeled this behavior as “spooky” as it doesn’t follow everyday logic.
Common sense tells us that objects across the universe cannot possibly be
connected, yet in the quantum realm, they are. Quantum mechanics also says that
properties of particles are only fixed when the particle is observed.
Some
physicists, including Albert Einstein, opposed this notion as it went against
the very nature of the real world. In the 1930s when quantum mechanics was an
emerging field, Einstein was a proponent of “local realism,” arguing that only
close objects could affect each other. Einstein and other physicists developed the
‘hidden variables theory’ to explain the spooky behavior. They argued that our
knowledge of quantum mechanics was incomplete and there could be hidden
variables that we didn’t yet understand.
physicists, including Albert Einstein, opposed this notion as it went against
the very nature of the real world. In the 1930s when quantum mechanics was an
emerging field, Einstein was a proponent of “local realism,” arguing that only
close objects could affect each other. Einstein and other physicists developed the
‘hidden variables theory’ to explain the spooky behavior. They argued that our
knowledge of quantum mechanics was incomplete and there could be hidden
variables that we didn’t yet understand.
In the 1960s
a physicist named John Bell devised a mathematical expression – called an
inequality – to test for these so-called hidden variables. He realized that if
these hidden variables did indeed exist, there would be a limit to how
connected the particles were. If they exceeded the set limit then the hidden variables
did not exist. However, the experiment – known as Bell’s Inequality – did not
definitively close the door on local realism.
The tests involved entangled
photons, which can get lost along the way, and experimenters might not detect
all photons produced.
a physicist named John Bell devised a mathematical expression – called an
inequality – to test for these so-called hidden variables. He realized that if
these hidden variables did indeed exist, there would be a limit to how
connected the particles were. If they exceeded the set limit then the hidden variables
did not exist. However, the experiment – known as Bell’s Inequality – did not
definitively close the door on local realism.
The tests involved entangled
photons, which can get lost along the way, and experimenters might not detect
all photons produced.
In the new
experiment, led by Professor Ronald Hanson of Delft University of Technology in
the Netherlands, we have two researchers – we will call them Alice and Bob – in
two laboratories 1.3 kilometers apart. Each laboratory is set up with a diamond
chip containing an electron whose spin was entangled with a photon. The photons
were then sent to a third lab in between Alice and Bob, where a detector
records the arrival time. If two photons arrived at the same time they would be
entangled, resulting in the electrons being entangled as well.
experiment, led by Professor Ronald Hanson of Delft University of Technology in
the Netherlands, we have two researchers – we will call them Alice and Bob – in
two laboratories 1.3 kilometers apart. Each laboratory is set up with a diamond
chip containing an electron whose spin was entangled with a photon. The photons
were then sent to a third lab in between Alice and Bob, where a detector
records the arrival time. If two photons arrived at the same time they would be
entangled, resulting in the electrons being entangled as well.
The
experiment took place over a span of nine days. In that time, researchers
recorded 245 successful entanglements. While other tests over the last few
decades have also supported Bell’s limit, this new experiment learns from their
shortcomings to overcome experimental pitfalls. Previous test used inefficient
detectors, only measuring a small number of the particles passing through them.
Recent experiments used near-perfect detectors, but the entangled particles were
close enough to potentially communicate. In the new experiment, the team used
high-quality detectors and measurements collected before the electrons could
possibly exchange signals with each other, making it the first to close both
loopholes.
experiment took place over a span of nine days. In that time, researchers
recorded 245 successful entanglements. While other tests over the last few
decades have also supported Bell’s limit, this new experiment learns from their
shortcomings to overcome experimental pitfalls. Previous test used inefficient
detectors, only measuring a small number of the particles passing through them.
Recent experiments used near-perfect detectors, but the entangled particles were
close enough to potentially communicate. In the new experiment, the team used
high-quality detectors and measurements collected before the electrons could
possibly exchange signals with each other, making it the first to close both
loopholes.
The results
of this experiment have big implications for the world of quantum cryptography
– meaning entangled photons could potentially create secure encryption keys.
Closing the loopholes would ensure that computer systems could detect if anyone
tried to intercept the keys, as it would break the entanglement and trigger an
alarm.
Source
of this experiment have big implications for the world of quantum cryptography
– meaning entangled photons could potentially create secure encryption keys.
Closing the loopholes would ensure that computer systems could detect if anyone
tried to intercept the keys, as it would break the entanglement and trigger an
alarm.
Source
