Quantum technology is an emerging field of physics and engineering, which relies on the principles of quantum physics. Quantum computing, quantum sensors, quantum cryptography, quantum simulation, quantum metrology and quantum imaging are all examples of quantum technologies, where properties of quantum mechanics, especially quantum entanglement, quantum superposition and quantum tunnelling, are important.
Quantum secure communication are methods which are expected to be 'quantum safe' in the advent of a quantum computing systems that could break current cryptography systems. One significant component of a quantum secure communication systems is expected to be Quantum key distribution, or 'QKD': a method of transmitting information using entangled light in a way that makes any interception of the transmission obvious to the user. Another technology in this field is the quantum random number generator used to protect data. This produces truly random numbers without following the procedure of the computing algorithms that merely imitate randomness.
Quantum computers are expected to have a number of important uses in computing fields such as optimization and machine learning. They are perhaps best known for their expected ability to carry out 'Shor's Algorithm', which can be used to factorise large numbers and is an important process in the securing of data transmissions.
There are many devices available today which are fundamentally reliant on the effects of quantum mechanics. These include laser systems, transistors and semiconductor devices and other devices, such as MRI imagers. The UK Defence Science and Technology Laboratory (DSTL) grouped these devices as 'quantum 1.0', that is devices which rely on the effects of quantum mechanics. These are generally regarded as a class of device that actively create, manipulate and read out quantum states of matter, often using the quantum effects of superposition and entanglement.
The field of quantum technology was first outlined in a 1997 book by Gerard J. Milburn, which was then followed by a 2003 article by Jonathan P. Dowling and Gerard J. Milburn, as well as a 2003 article by David Deutsch. The field of quantum technology has benefited immensely from the influx of new ideas from the field of quantum information processing, particularly quantum computing. Disparate areas of quantum physics, such as quantum optics, atom optics, quantum electronics, and quantum nanomechanical devices, have been unified in the search for a quantum computer and given a common "language", that of quantum information theory.
From 2010 onwards, multiple governments have established programmes to explore quantum technologies, such as the UK National Quantum Technologies Programme, which created four quantum 'hubs', the Centre for Quantum Technologies in Singapore, and QuTech, a Dutch centre to develop a topological quantum computer. In 2016, the European Union introduced the Quantum Technology Flagship, a €1 Billion, 10-year-long megaproject, similar in size to earlier European Future and Emerging Technologies Flagship projects.  In December 2018, the United States passed the National Quantum Initiative Act, which provides a US$1 billion annual budget for quantum research. China is building the world's largest quantum research facility with a planned investment of 76 Billion Yuan (approx. €10 Billion).
In the private sector, large companies have made multiple investments in quantum technologies. Examples include Google's partnership with the John Martinis group at UCSB, multiple partnerships with the Canadian quantum computing company D-wave systems, and investment by many UK companies within the UK quantum technologies programme.