How Quantum Computers Work
Defining the Quantum Computer
Quantum computing is the use of quantum-mechanical phenomena such as superposition and entanglement to perform computation. A quantum computer is used to perform such computation, which can be implemented theoretically or physically. The Turing machine, developed by Alan Turing in the 1930s, is a theoretical device that consists of tape of unlimited length that is divided into little squares. Each square can either hold a symbol (1 or 0) or be left blank. A read-write device reads these symbols and blanks, which gives the machine its instructions to perform a certain program. In a quantum Turing machine, the difference is that the tape exists in a quantum state, as does the read-write head. This means that the symbols on the tape can be either 0 or 1 or a superposition of 0 and 1; in other words the symbols are both 0 and 1 (and all points in between) at the same time. While a normal Turing machine can only perform one calculation at a time, a quantum Turing machine can perform many calculations at once.
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Today's computers, like a Turing machine, work by manipulating bits that exist in one of two states: a 0 or a 1. Quantum computers aren't limited to two states; they encode information as quantum bits, or qubits, which can exist in superposition. Qubits represent atoms, ions, photons or electrons and their respective control devices that are working together to act as computer memory and a processor. Because a quantum computer can contain these multiple states simultaneously, it has the potential to be millions of times more powerful than today's most powerful supercomputers.
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This superposition of qubits is what gives quantum computers their inherent parallelism. According to physicist David Deutsch, this parallelism allows a quantum computer to work on a million computations at once, while your desktop PC works on one. A 30-qubit quantum computer would equal the processing power of a conventional computer that could run at 10 teraflops (trillions of floating-point operations per second). Today's typical desktop computers run at speeds measured in gigaflops (billions of floating-point operations per second).
Quantum computers also utilize another aspect of quantum mechanics known as entanglement. One problem with the idea of quantum computers is that if you try to look at the subatomic particles, you could bump them, and thereby change their value.
If you look at a qubit in superposition to determine its value, the qubit will assume the value of either 0 or 1, but not both (effectively turning your spiffy quantum computer into a mundane digital computer). To make a practical quantum computer, scientists have to devise ways of making measurements indirectly to preserve the system's integrity. Entanglement provides a potential answer. In quantum physics, if you apply an outside force to two atoms, it can cause them to become entangled, and the second atom can take on the properties of the first atom. So if left alone, an atom will spin in all directions. The instant it is disturbed it chooses one spin, or one value; and at the same time, the second entangled atom will choose an opposite spin, or value. This allows scientists to know the value of the qubits without actually looking at them.
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IBM Unveils Q System One Quantum Computer
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https://www.extremetech.com/extreme/283427-quantum-computing-goes-commercial-with-ibms-q-system-one
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Quantum computing still seems like it comes from the pages of a science fiction novel, but it is slowly getting closer to being a commercial reality. At CES 2019, IBM Research has made what it hopes is a big step in that direction with what it calls the “first fully-integrated commercial quantum computer,” the Q System One. Existing quantum computers are confined to R&D labs, while the Q System One includes both the electronics and cooling components needed in a single package that was developed in concert with leading industrial designers. ....
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Using 'solid' light in computing:
https://www.pnas.org/content/113/35/9740
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STRANGE PHASE OF MATTER DISCOVERED TO REDUCE ERRORS AND RETAIN DATA LONGER
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By firing a Fibonacci laser pulse at atoms inside a quantum computer, physicists have created a completely new, strange phase of matter that behaves as if it has two dimensions of time.
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The new phase of matter(opens in new tab), created by using lasers to rhythmically jiggle a strand of 10 ytterbium ions, enables scientists to store information in a far more error-protected way, thereby opening the path to quantum computers(opens in new tab) that can hold on to data for a long time without becoming garbled. The researchers outlined their findings in a paper published July 20 in the journal Nature.
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To test how important imaginary numbers were in describing reality, the researchers used an updated version of the Bell test, an experiment which relies on quantum entanglement. (Image credit: Jurik Peter via Shutterstock)
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The Bloch sphere is a representation of a qubit,
the fundamental building block of quantum computers.
