The Islamic State of Iraq and the Levant is proscribed as a terrorist organisation by the United Kingdom. British citizens have fought as members of the group, there has been political debate on how to punish them. On 26 September 2014, Parliament voted to begin Royal Air Force airstrikes against ISIL in northern Iraq at the request of the Iraqi government, which began four days using Tornado GR4 jets. On 2 December 2015, the UK Parliament authorised an extension to the Royal Air Force airstrike campaign, joining the US-led international coalition against ISIL in Syria. Hours after the vote, Royal Air Force Tornado jets began bombing ISIL-controlled oilfields. William Hague Foreign Secretary, estimated in June 2014 that 400 British citizens were fighting in Syria, some for ISIL. Khalid Mahmood, a Labour MP, estimated that there were at least 1,500 Britons in ISIL. A more accurate source from the BBC estimates around 850 people from the UK had traveled to Iraq and Syria to support or fight for jihadist groups.
Former MI6 counter-terrorism head Richard Barrett raised concerns about the large number of radicalised fighters that had returned to Britain from Syria and Iraq. Journalist James Foley was executed around 19 August 2014, on video by an ISIL member whose accent sounded English; the killer, Mohammed Emwazi, was described in the media as "Jihadi John". In August 2014, activists in London handed out leaflets in support of ISIL outside the busy Oxford Circus branch of Topshop. A sacked colonel of Bangladesh army is one of the major operative residing in London. On 7 September 2015, a Royal Air Force MQ-9 Reaper drone conducted an airstrike in Syria which killed two British-born ISIL fighters. On 24 October 2017, it was announced that a British man, fighting against Isil with the Kurdish YPG in Raqqa had been killed whilst trying to clear land mines; this took the total number of British volunteers fighting Isis in Syria to six. The British government proscribed ISIL as a terrorist organisation in June 2014.
It had been proscribed as a part of Al-Qaeda. The government describes the group as follows: ISIL is a brutal Sunni Islamist terrorist group active in Iraq and Syria; the group adheres to a global jihadist ideology, following an extreme interpretation of Islam, anti-Western and promotes sectarian violence. ISIL aims to establish an Islamic State governed by Shari'a law in the region and impose their rule on people using violence and extortion. In August 2014, British Prime Minister David Cameron suggested that anybody displaying the black standard in the United Kingdom should be arrested. Home Secretary Theresa May suggested new measures against radical preachers, stripping citizenship from naturalised Britons who fought for ISIL, trying British-born ISIL members for engaging in terrorism abroad. Other figures, such as Mayor of London Boris Johnson, Conservative backbench MP David Davis, former Archbishop of Canterbury Lord Carey and UKIP leader Nigel Farage have stated that all British citizens in ISIS should lose their citizenship.
On 29 August 2014, the UK terror threat was raised from "substantial" to "severe". Sir Malcolm Rifkind, a senior MP, advocated an alliance with President Bashar al-Assad of Syria to defeat ISIL; this was ruled out by Foreign Secretary Philip Hammond, who stated "We may well find that we are aligned against a common enemy. But that does not make us able to trust them, it does not make us able to work with them and it would poison what we are trying to achieve in separating moderate Sunni opinion from the poisonous ideology of if we were to align ourselves with President Assad."Royal Air Force Tornado jets and Chinook helicopters based in Cyprus have provided humanitarian aid to Yazidi refugees fleeing ISIL, as well as airlifts. The Beatles
In physics, the Rabi cycle is the cyclic behaviour of a two-level quantum system in the presence of an oscillatory driving field. A great variety of physical processes belonging to the areas of quantum computing, condensed matter and molecular physics, nuclear and particle physics can be conveniently studied in terms of two-level quantum mechanical systems, exhibit Rabi flopping when coupled to an oscillatory driving field; the effect is important in quantum optics, magnetic resonance and quantum computing, is named after Isidor Isaac Rabi. A two-level system has two possible levels, if they are not degenerate, the system can become "excited" when it absorbs a quantum of energy; when an atom is illuminated by a coherent beam of photons, it will cyclically absorb photons and re-emit them by stimulated emission. One such cycle is called a Rabi cycle and the inverse of its duration the Rabi frequency of the photon beam; the effect can be modeled using the Jaynes -- the Bloch vector formalism. A detailed mathematical description of the effect can be found on the page for the Rabi problem.
For example, for a two-state atom in an electromagnetic field with frequency tuned to the excitation energy, the probability of finding the atom in the excited state is found from the Bloch equations to be: | c b | 2 ∝ sin 2 ,where ω is the Rabi frequency. More one can consider a system where the two levels under consideration are not energy eigenstates. Therefore, if the system is initialized in one of these levels, time evolution will make the population of each of the levels oscillate with some characteristic frequency, whose angular frequency is known as the Rabi frequency; the state of a two-state quantum system can be represented as vectors of a two-dimensional complex Hilbert space, which means every state vector | ψ ⟩ is represented by good complex coordinates. | ψ ⟩ = = c 1 + c 2. If the vectors are normalized, c 1 and c 2 are related by | c 1 | 2 + | c 2 | 2 = 1; the basis vectors will be represented as | 0 ⟩ = and | 1 ⟩ = All observable physical quantities associated with this systems are 2 × 2 Hermitian matrices, which means the Hamiltonian of the system is a similar matrix.
One can construct an oscillation experiment through the following steps: Prepare the system in a fixed state. If the two states | 0 ⟩ and | 1 ⟩ are degenerate, every state including | 1 ⟩ is an eigenstate of H; as a result, there will be no oscillations. On the other hand, if H has no degenerate eigenstates, the initial state is not an eigenstate there will be oscillations; the most general form of the Hamiltonian of a two-state system is given H = here, a 0, a 1, a 2 and a