A quantum computer is a computer that uses quantum mechanical phenomena to perform calculations. These computers are different in many ways from the computers that are in use today. For example, a quantum computer can be in multiple states simultaneously, whereas a classical computer can only be in one state at a time. This allows quantum computers to perform several calculations at once.

#### What do quantum computers do?

A quantum computer is a computer that uses quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. A quantum computer operates on qubits, which are units of quantum information.

Quantum computers are different in many ways from traditional computers. Traditional computers use bits that are either 1 or 0. Quantum computers use qubits that can be both 1 and 0 simultaneously, due to the phenomenon of superposition. This allows for many calculations to be done at the same time, which is why quantum computers are often said to be "faster" than traditional computers.

Another difference is that traditional computers use logic gates to perform operations on data. Quantum computers use quantum gates, which are different in many ways. For example, a quantum NOT gate (also called a CNOT gate) can entangle two qubits, so that the state of one qubit is always the inverse of the state of the other qubit. This is not possible with traditional logic gates.

Quantum computers have the potential to solve certain problems much faster than traditional computers. For example, quantum computers can efficiently solve problems in quantum chemistry and machine learning. Does there exist a quantum computer? Yes, there exist quantum computers. As of 2021, Google, IBM, and Microsoft all offer quantum computing services that anyone can access through the cloud. Does NASA have a quantum computer? As of September 2020, NASA does not have a quantum computer, but is interested in the technology and is collaborating with research organizations to develop it. In July 2019, NASA awarded a $1.1 million contract to D-Wave Systems to explore the feasibility of using quantum computers for aeronautical applications.

Who uses quantum computers? Quantum computers are still in development and not yet widely available, so there are not many people who use them. However, there are a few organizations that have access to quantum computers, and they are typically used for research purposes. For example, Google has a quantum computer that it uses for research into artificial intelligence and machine learning.

##### How fast is a quantum computer?

A quantum computer is a computer that uses quantum-mechanical phenomena, such as superposition and entanglement, to perform operations on data. A quantum computer operates on qubits, which are units of quantum information.

The speed of a quantum computer is limited by the coherence time of the qubits. The coherence time is the time over which the quantum state of a qubit remains coherent. Coherence times are typically very short, on the order of nanoseconds or less. This means that quantum computers are not yet able to perform large-scale quantum computations.