Page 45 - GCN, March and April 2017

before we run,” he added, noting that quantum demonstrations would lead to more complex applications.
In another parallel between digital and quantum computing, the potential of the former was not fully appreciated in the 1960s. “We see the same type of potential now for quantum comput- ing,” Polk said.
Despite his optimism, he warned that the country’s lead in quantum technol- ogy is under siege from researchers in Canada, Europe and China. For ex- ample, a Chinese satellite launched last summer, dubbed Quantum Experiments at Space Scale, seeks to demonstrate hack-proof satellite communications based on the ephemeral properties of
quantum physics, including the myste- rious phenomenon known as quantum entanglement.
Wisnieff noted that Chinese research- ers are making heavy use of IBM’s cloud-based quantum platform. •
— George Leopold is a contributing editor for GCN’s sister publication Defense Systems.
How quantum computing works
Devices based on subatomic physics could make calculations far faster than conventional machines — if nothing spoils their quantum weirdness.
UNDERSTANDING THE QUBIT
COMPUTING A MOVING TARGET
1 QUANTUM COMPUTATION USING ENTANGLEMENT Data is spread across entangled qubits, which are isolated from the environment.
PERFORM COMPUTATION
AFTER COMPUTATION
The entangled qubits have processed their information in parallel.
2 QUANTUM COMPUTATION USING DISCORD Only one qubit is protected from the environment.
0
QUBITS
BITS
A classical computer uses binary encoding, where a bit can take one of two values: 0 or 1.
1
0
1
1
0
Quantum bits, or qubits, can be encoded by, say, the up or down spin of a particle, and can exist as a superposition of 0 and 1 simultaneously (represented by the sphere).
0
0
1
0
0
0
1
11
1
When it is measured, a qubit will collapse into a 0 or 1. The probability of each outcome depends on where the qubit is on the sphere.
0
70%
MEASUREMENT
30%
Source: Nature.com
PERFORM COMPUTATION
AFTER COMPUTATION
The other qubits have been exposed to noise and disruption.
1
0
1
One qubit serves as spokesman. Taking an average of measurements (0 or 1) over many runs gives the answer.
Measuring the protected qubit and averaging over many runs also gives the right answer.
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