CN108415206A - The light pulse generation method of the arbitrary superposition state of three-lever system quantum bit can be created - Google Patents

Abstract

The invention discloses the light pulse generation methods that can create the arbitrary superposition state of three-lever system quantum bit, using the time-dependent Schrodinger equation of the Converse solved three-lever system of invariant theory, structure can generate the field intensity information of one group of double-colored light pulse of the arbitrary superposition state of quantum bit, use Arbitrary Waveform Generator and acousto-optic modulator, generate double-colored light pulse, the extra discretion of bi-coloured light pulsed field persistent erection is used to optimize the shape of pulse, it is allowed to show robustness to frequency detuning present in system, it is sufficiently small to the off-resonance excitation of background ions present in system, to which the arbitrary superposition state of quantum bit is created with fidelity within short action time；The light pulse that the present invention generates can generate the arbitrary superposition state of a quantum bit within the action time of 4 μ s, and the fidelity within the scope of the frequency detuning of ± 340kHz is not less than 99.5%, be no more than 2% to the off-resonance excitation of background ions.

Description

Optical pulse generation method for creating arbitrary superposition states of qubits in three-level systems

technical field

The invention belongs to the field of quantum computing, and in particular relates to an optical pulse capable of manipulating a quantum system to generate any superposition state of qubits.

Background technique

Quantum computing is an important branch of quantum information processing. It has an unmatched computing speed of classical computing algorithms in problems such as factorization of large prime numbers, global search, and biomolecular simulation. Initializing a qubit into an arbitrary superposition state with high fidelity in a short time using pulses of light is the first step towards unlocking quantum computing. However, some interference factors inevitably exist in the physical system, such as frequency detuning, optical field intensity fluctuations, optical field phase fluctuations, non-resonant excitation and other interferences. How to generate light pulses so that they are robust to these disturbances when manipulating qubits, and at the same time have the characteristics of short action time and high fidelity is an urgent problem in the field of quantum computing.

In many physical systems carrying quantum computing, rare earth ions randomly doped in inorganic crystals are a more competitive carrier, because the coherence time of qubits can be as long as 6 hours, and the crystals are cheap and already available. commoditization. In this system, the qubit is characterized by a group of ensemble ions on the non-uniform broadening line. Taking Pr ³⁺ doped in Y ₂ SiO ₅ crystal as an example, their optical transition frequency at 605.977nm exhibits ± Full width at half maximum of 170kHz. The coupling between the two energy levels of the qubit is implemented through optical transitions, forming a three-level system. To create an arbitrary superposition state of a qubit with high fidelity in such a three-level system, the light pulse must satisfy the following conditions, (1) the fidelity of the manipulation of the qubit versus the frequency mismatch that exists between the qubit ions The quantity exhibits strong robustness, that is, the fidelity is as close as possible to the ideal value 1 in the range of ±170kHz; (2) the non-resonant excitation of other ions that are more than 3.5MHz away from the qubit ion in the frequency domain is sufficiently small , so as not to interfere with qubit ions; (3) The pulse action time is as short as possible.

There are currently three main types of light pulses used to manipulate quantum systems. The first is a simple resonant pulse, such as square wave pulse, Gaussian pulse, etc. This kind of pulse has a short action time, but it is more sensitive to the interference factors in the system. The second is the adiabatic approximate light pulse, which has better robustness to the interference factors existing in the system, but because it is an adiabatic process, the pulse action time is longer. The third is the adiabatic short-cut optical pulse based on the non-adiabatic process, which has been proved in some physical systems to realize the quantum layout number transfer with high fidelity and strong robustness in a short action time. However, the layout number transfer is only a special state in the arbitrary superposition state of qubits, and the arbitrary superposition state is a common state that is indispensable in quantum manipulation and can fully exploit the powerful computing capabilities of quantum computers. At present, in a three-level quantum system with frequency detuning, such as a rare-earth ion system, it has not been reported to generate light pulses in any superposition state of qubits with high fidelity in a short period of time.

Contents of the invention

The technical problem solved by the present invention is: the pulse action time is too long and the robustness is poor; the present invention seeks a method for generating a group of two-color light pulses, the two-color light pulses are composed of two pulses with equal duration and different amplitudes, frequencies and phases. Composed of pulses, the two act on a three-level quantum system composed of two qubit energy levels and an excited state energy level at the same time, and the quantum system can be manipulated to generate any superposition state of qubits from the initial state |1> where θ _a ∈ [0, π], Under certain conditions, the generated light pulses have the following characteristics:

A. The pulse action time is short, under the premise that the pulse Rabi frequency does not exceed 2MHz, the action time does not exceed 4μs;

B. The fidelity of generating any superposition state of qubits is not less than 99.5%;

C. Robust to frequency detuning present in quantum systems over a range of at least ±170 kHz;

D. No more than 2% off-resonant excitation of ions other than the center frequency of the qubit ion at 3.5 MHz.

In order to achieve the above object, the technical scheme adopted in the present invention is as follows:

A light pulse generation method that can create any superposition state of qubits in a three-level system. In a three-level system, the amplitude and phase of the light pulse are obtained by inversely solving the time-dependent Schrödinger equation of the three-level system based on the Lewis-Riesenfeld invariant theory , input this amplitude and phase into the arbitrary wave generator to generate a radio signal with the same amplitude and phase as the optical pulse, use this radio signal to drive the acousto-optic modulator in the continuous laser optical path to obtain +1 or -1 deflection output light , generating a set of two-color light pulses.

The generated two-color light pulse is vertically incident on the three-level quantum system medium, and the two-color light pulse interacts with the quantum system medium to generate any superposition state of qubits. Compared with the prior art, the present invention has the following salient features:

The generated two-color light pulse is suitable for a three-level quantum system, including two simultaneous light pulses with different frequencies, amplitudes and phases. The above parameters of the light pulse can be fully controlled by the arbitrary wave generator and the acousto-optic modulator. .

Two-color light pulses can generate an arbitrary superposition state of a qubit in a three-level system, including arbitrary layout number distribution and arbitrary relative phase control between two qubit energy levels.

The start and end values of the two-color light pulse can be zero or not, and any superposition state of qubits can be generated.

The amplitude of the dichromatic light pulse varies with time, but the frequency and phase do not.

The duration of the optical pulse can be arbitrarily short in theory, as long as the intensity of the optical field is large enough. For an optical field with a maximum Rabi frequency of 2 MHz, the length of the optical pulse does not exceed 4 μs.

Description of drawings

Figure 1 is a related energy level structure diagram of Pr ³⁺ doped in Y ₂ SiO ₅ crystal;

Figure 2 is a diagram of the Rabi frequency of the light pulse changing with time during the process of the light pulse interacting with the quantum system;

Figure 3 is a state evolution diagram of the qubit during the light pulse interacting with the quantum system;

Figure 4 is a graph showing the Rabi frequency of the light pulse changing with time during the process of the light pulse interacting with the quantum system;

Fig. 5 is a time-dependent diagram of the state of the qubit in the process of the light pulse interacting with the quantum system;

Fig. 6 is a diagram of the Rabi frequency changing with time when the light pulse interacts with the quantum system;

Fig. 7 is a time-dependent diagram of the state of the qubit in the process of the light pulse interacting with the quantum system;

Fig. 8 is a dependence diagram between the fidelity of the target qubit superposition state and the amount of frequency detuning generated by the light pulse after the interaction with the quantum system;

Figure 9 is a diagram of the non-resonant excitation of background ions at a distance of ΔMHz from qubit ions after the light pulse interacts with the quantum system;

Figure 10 is a diagram of the Rabi frequency changing with time during the action of the light pulse on the quantum system;

Fig. 11 is a dependence diagram between the fidelity of the target quantum state and the amount of frequency detuning generated by the light pulse after the interaction with the quantum system;

Figure 12 is a diagram of the non-resonant excitation of the background ions at a distance of ΔMHz from the qubit ions after the light pulse interacts with the quantum system;

Among them, Ω _p in the figure is the Rabi frequency of the optical transition from energy level |2> to energy level |e>; Ω _s is the Rabi frequency of the optical transition from energy level |0> to energy level |e>; is the phase of the optical transition from |0> to the energy level |e>; t is the pulse action time; P _m is the probability of the ion in the |m> state at time t; m=0,1,e; F is the target state Fidelity; Δ is the amount of off-resonance frequency detuning.

Detailed ways

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Embodiment one:

An optical pulse generation method that can create arbitrary superposition states of qubits in a three-level system, according to the initial state |1> and the target state of the system where θ _a is in the range [0, π], Take the value in the range of [0, 2π], use the adiabatic shortcut technology based on the Lewis-Riesenfeld invariant theory to reversely solve the time-dependent Schrödinger equation of the three-level system to obtain the amplitude and phase of the two optical pulses, and input the amplitude and phase The arbitrary wave generator generates a radio signal with the same amplitude and phase as the optical pulse, and uses this radio signal to drive the acousto-optic modulator in the continuous laser optical path to obtain +1 or -1 deflected output light, generating a set of two-color optical pulses;

Where: the driving frequency of the acousto-optic modulator is f _aom , the laser frequency in the continuous laser light path is f _laser , the qubit is characterized by two energy levels |0> and |1>, and the frequency difference between them is f _0-1 , the optical transition frequency of electrons from energy level |1> to energy level |e> is ν _p , the optical transition frequency of electrons from energy level |0> to energy level |e> is ν _s , driving acousto-optic The frequency of the radio signal that the modulator generates the optical pulse acting on the |1>-|e> transition is f _p , and the frequency of the radio signal that drives the acousto-optic modulator to generate the optical pulse acting on the |0>-|e> transition is f _s , the two satisfy f _p =f _aom , f _s =f _aom +f _0-1 ; f _laser+ f _p =ν _p ; the phases of the two radio signals are expressed as: and The amplitudes are expressed as: E _p and E _s ;

Then satisfy: Both E _p and E _s vary with time, determined by the following relationship:

where μ _p,s is the transition dipole moment of |1>-|e> and |0>-|e> optical transition; Ω _p,s is the Rabi frequency of the two optical pulses; C is the The conversion coefficient of the Rabi frequency Ω _p,s to the radio signal amplitude E _p,s is determined by the experimental system; the Rabi frequency Ω _p,s depends on the time t as shown in the following formula:

In the formula and is the differential of functions β(t) and γ(t) with respect to time; where γ(t) is formed by superposition of a series of Fourier components:

In the formula, t _f is the duration of the pulse (in seconds); n is a positive integer; a _n is the coefficient of the corresponding Fourier component, and β(t) depends on γ(t) as shown in the following formula:

The amplitude of the two-color light pulse generated by the above technical solution contains 8 degrees of freedom (a _n , n=1, 2, 3...8), adjusting the value of a _n in the range of real numbers can generate light pulses with different performances; The _two -color light pulse generated when a takes any real value is only suitable for quantum systems without frequency detuning and non-resonant excitation, and any superposition state of qubits can be generated in this quantum system.

Accompanying drawing 1 is doped in Y ₂ SiO ₅ in the Pr ³⁺ related energy level structure diagram, take it as an example to illustrate the applicable three-level system of this technical scheme; Among the figure ground state and excited state respectively comprise three Hyperfine energy level, |e> is an excited state, |0> and |1> are two energy levels that characterize qubits, and the coupling between them is through |1>-|e> and |1>-| e>Two optical transitions are implemented.

target state For example, that is, θ _a = π/4, To illustrate the shape of the light pulse and its working performance. The aforementioned two-color light pulse is substituted into the coupled differential equation describing the interaction between light and the three-level quantum system, and the working performance of the light pulse is simulated in Matlab. The fidelity F to generate the qubit target state is defined as follows:

F＝|<ψ _target |ψ(t _f )>| ²

Where |ψ(t _f )> is the state function of the quantum state |ψ(t)> obtained by solving the three-level coupled differential equation at time t=t _f .

At the end of the interaction between the light pulse and the quantum system, the non-resonant excitation of the background ions by the light pulse is characterized by the probability P _m of |ψ(t _f )>in the |1> state, |0> state and |e> state, where The expression is:

P _m ＝|<m|ψ(t _f )>| ²

where m=0,1,e.

Embodiment two:

In the light pulse generation method that can create any superposition state of three-level system qubits based on the first embodiment, all values of a _n in formula (4) are zero. at this time:

Based on this γ(t) and β(t) shown in the formula (5), the Rabi frequency of the light pulse generated by the formulas (2) and (3) is shown in Figure 2, where the solid line is _Ωp and the dashed line is Ω _s , the pulse action time is 4μs, the start and end values of the Rabi frequency are not equal to zero, and the maximum instantaneous Rabi frequency does not exceed 0.5MHz.

Figure 3 shows the evolution of the quantum state |ψ(t)> over time during the interaction between the pulse and the detuned quantum system. At the initial moment, the quantum state is in the |1>state; at the end of the pulse, that is, t=4μs, the probability of the quantum state in both |0> and |1> is 50%, which is the same as the target state match.

In this embodiment, the optical pulse produces the target quantum state |ψ _target 〉 with fidelity F=1, but this two-color optical pulse is only applicable to the quantum system without frequency detuning and non-resonant excitation.

The advantage of the optical pulse produced in this embodiment is that the absolute value of the required instantaneous Rabi frequency does not exceed 0.5MHz, which is an advantage for quantum systems with limited optical field strength; The value is not zero, which requires that the response speed of the acousto-optic modulator in the system is fast enough, and there are no background ions or atoms that may be excited near the center frequency of the qubit.

Embodiment three:

In the light pulse generation method that can create any superposition state of three-level system qubits based on the first embodiment, all even and odd terms of a _n in formula (4) satisfy the following two conditions respectively:

a ₁ +3a ₃ +5a ₅ +7a ₇ = 0,

a ₂ +2a ₄ +3a ₆ +4a ₈ = -0.5.

Then the Rabi frequencies of the two light pulses at the initial and final moments are zero, that is, Ω _p,s (t=0,tf)=0. By substituting any a _n value that satisfies these two relations into the formula (4), the constructed light pulse can manipulate the quantum system to create the target state |ψ _target >, here in the simplest case a ₂ =-0.5, a _{1.3.4.5 .6.7.8} = 0 as an example, explain the shape of the light pulse and its working performance.

Accompanying drawing 4 is the Rabi frequency of the two-color light pulse in this embodiment, the values at the initial and termination moments are all zero, avoiding the multiple Fourier frequencies brought in the frequency domain by the sharp change of the field intensity at the endpoint The possible effects of components on qubits in quantum systems in the presence of background ions.

Figure 5 shows the evolution of the quantum state over time during the interaction between the two-color light pulse and the non-detuning quantum system in this embodiment. The initial state of the system is |1>, and the probabilities of the final state are both |0> and |1> are 50%.

In this embodiment, the optical pulse produces the target quantum state |ψ _target > with fidelity F=1, but the two-color optical pulse is only applicable to the quantum system without frequency detuning and non-resonant excitation.

The advantage of the optical pulse produced in this embodiment is that the absolute value of the required instantaneous Rabi frequency increases compared with Embodiment 2, but it is still less than 1MHz, which is an advantage for quantum systems with limited optical field strength; the Rabi frequency is at The values at the initial and end moments are zero, and change slowly with time, which reduces the requirement for the response time of the acousto-optic modulator; during the pulse action, the ion is in the excited state for about 1.2 μs, while the coherent Pr ion The time is as long as 150μs, which effectively reduces the possibility of decoherence.

Embodiment four:

The optical pulse generation method based on the first embodiment can create any superposition state of qubits in the three-level system, by scanning the value of a _n , at the end of the interaction between the optical pulse and the quantum system, the fidelity and the fidelity of the generated target state are detected The relationship between non-resonant excitation of background ions and the variation of frequency detuning amount, the optimal value of a _n in formula (4) is obtained. For example: a _1.3.5.7 = 0, a ₂ = -1.10, a ₄ = 0.09, a ₆ = 0.06, and a ₈ = 0.06, the Rabi frequency of the optical pulse generated based on these parameters is shown in Fig. 6 . The pulse action time is still 4 μs, and the Rabi frequency is increased compared with Embodiment 1 and Example 2, but the maximum Rabi frequency is still less than 1.5 MHz.

Figure 7 shows the evolution of the quantum state over time during the interaction between the optical pulse generated in this embodiment and the quantum system without detuning. At the initial moment the quantum state is in the |1> state, and at the end of the pulse t=4μs, the probability of the quantum state being in both |0> and |1> is 50%.

Accompanying drawing 8 is when the optical pulse generated in this embodiment interacts with the quantum system with frequency detuning, the fidelity F of the target quantum state |ψ _target > is changed with the frequency detuning amount Δ. Where Δ is the difference between the center frequency of the light pulse and the corresponding transition frequency of the qubit ions or background ions, that is, the amount of detuning of the non-resonant frequency. When there is no frequency detuning, that is, Δ=0, the fidelity is 1; in the range of ±340kHz near the center frequency, the fidelity F>99.5%, showing strong robustness; for the rare earth shown in Figure 1 For ionic systems, the robustness in the ±340kHz range is sufficient because the full width at half maximum of the qubit absorption peak is 170kHz; otherwise, the fidelity behavior between ±340kHz and 3.5MHz is irrelevant because the qubit The ions are located in a frequency window with zero absorption, and the center frequency of the bit ions is approximately 3.5 MHz from the boundary of the frequency window. For background ions whose detuning exceeds 3.5 MHz, the value of fidelity has no meaning for quantum calculations and their behavior is not considered.

Figure 9 shows the non-resonant excitation of the background ions at a distance of ΔMHz from the qubit ions when the light pulse interacts with the quantum system, which is reflected in the distribution ratio P _m of the ions in the three energy states at the end of the pulse. For the rare earth ion system shown in Figure 1, the non-resonant excitations beyond 3.5 MHz are of interest. The ideal situation is that the light pulse does not excite the ions of |Δ|≥3.5MHz, that is, does not touch their state, and is still in the initial state |1> state. At Δ=±3.5MHz, about 1.9% probability ions are transferred from the initial state |1> to the |0> state, and the probability of being in the |e> state is zero. Considering that the background ion density at this frequency detuning amount is only 1/6 of the qubit ion density, the 1.9% transfer probability is small enough to cause negligible interference to the qubit ions.

The advantage of the optical pulse generated in this embodiment is that the fidelity of the manipulation of the pulse and the state of the qubit is strong, and it is robust to the frequency mismatch between the laser frequency and the qubit ion. The presence of off-resonant excitations in the vicinity of ions is sufficiently small, which is a key element for quantum computing in quantum systems with frequency detuning and off-resonance excitations; the time that ions are in the excited state during the pulse is further reduced, about 0.63 μs , which further reduces the chance of decoherence.

Embodiment five

Based on Embodiment 4, the optical pulse method of generating the target state |1> state from the initial qubit arbitrary superposition state in the three-level system, the following changes are made:

t→t _f -t,Ω _p,s →-Ω _p,s

That is to say, the amplitudes of the two light fields change inversely with time, and the phases increase by 180 degrees at the same time, and the others remain unchanged to generate a new set of two-color light pulses. This light pulse acts on the quantum system and can realize superposition from any qubit state Create |ψ _target >= |1> state. here to Take an example to illustrate the working performance of the light pulse.

Accompanying drawing 10 is the relationship diagram of the Rabi frequency of the light pulse in this embodiment with time.

Accompanying drawing 11 is when the optical pulse in this embodiment interacts with the quantum system with frequency detuning, from the initial state of the qubit where |Δ|≤3.5MHz, and the initial state of background ions |ψ _in >=|1>, where |Δ|>3.5MHz, the variation of the fidelity F of the target quantum state |1> with the frequency detuning Δ relation. When there is no frequency detuning, that is, Δ=0, the fidelity is 1; in the range of ±340kHz near the center frequency, F>99%, showing better robustness. The step change in fidelity at 3.5MHz is caused by the different initial states on both sides, because for the quantum system shown in Fig. 1, the initial state of ions with |Δ|≥3.5MHz is is always the |1> state, only the initial state of the qubit varies depending on the situation.

Accompanying drawing 12 is the non-resonant excitation situation graph of the background ion of Δ MHz to the distance qubit ion when the light pulse in this embodiment is interacting with the quantum system. When Δ=±3.5 MHz, about 0.3% of the ion Deviating from the initial superposition state, the probability of being on the |e> state is zero. A deviation of 0.3% causes negligible disturbance to the qubit ions.

The advantages of the light pulse generated in this embodiment are the same as those in Embodiment 4, the difference between the two is that the quantum manipulation process in this embodiment is to generate |1> state from an arbitrary superposition state.

The two-color light pulses generated by the above technical solutions can be used to make quantum computers or quantum memories based on rare earth ions. The components of these two devices include: a quantum system doped with rare earth ions, providing a low temperature environment for the quantum system to maintain its long-term coherence Time 2K cryostat, continuous laser output laser, the optical pulse generation system mentioned above, including arbitrary wave generator, acousto-optic modulator, and some common optical components such as mirrors, lenses, wave plates, polarizers Wait. It is worth pointing out that although this technical solution is developed for the three-level system, under certain conditions, the three-level system can be collapsed into a two-level system, so that the layout number transfer of the two-level system can be constructed. and light pulses that create a superposition state. These technical minor variations or modifications still belong to the category covered by the present invention.

Parts not described in detail in this technical solution belong to the well-known technology of those skilled in the art.

Claims (9)

1. the light pulse generation method of the arbitrary superposition state of three-lever system quantum bit can be created, adopted in a three-lever system Two light are obtained with the time-dependent Schrodinger equation based on the Converse solved three-lever system of Lewis-Riesenfeld invariant theories This amplitude and position are mutually inputted Arbitrary Waveform Generator generating amplitude and position phase nothing identical with light pulse by the amplitude and position phase of pulse Line electric signal drives the acousto-optic modulator in continuous laser light path to obtain+1 grade or -1 grade of deviation output using this radio signal Light generates one group of double-colored light pulse.

2. the light pulse generation method according to claim 1 for creating the arbitrary superposition state of three-lever system quantum bit, The double-colored light pulse of generation is impinged perpendicularly in three-level quantized system medium, double-colored light pulse and quantized system medium are mutual Effect generates the arbitrary superposition state of quantum bit.

3. the light pulse generation method according to claim 1 for creating the arbitrary superposition state of three-lever system quantum bit, According to the initial state of system | 1>With target stateWherein θ_aIn [0, π] range,The value in [0,2 π] range, it is Converse solved using the adiabatic shortcut technology based on Lewis-Riesenfeld invariant theories The time-dependent Schrodinger equation of three-lever system；

Wherein：The driving frequency of acousto-optic modulator is f_aom, laser frequency is f in continuous laser light path_laser, the quantum ratio Spy is by two energy levels | and 0>With | 1>It characterizes, difference on the frequency between them is f_0-1, electronics is from energy level | and 1>To energy level | e>Light jump It is ν to move frequency_p, electronics is from energy level | and 0>To energy level | e>Optical transition frequency be ν_s, driving acousto-optic modulator act in | 1>- |e>The frequency of the radio signal of the light pulse of transition is f_p, driving acousto-optic modulator act in | 0>-|e>The light of transition The frequency of the radio signal of pulse is f_s, the two meets f_p=f_aom, f_s=f_aom+f_0-1；f_laser+f_p=ν_p；Two aerograms Number position be mutually expressed as：WithAmplitude amplitude is expressed as：E_pAnd E_s；

Then meet：E_pAnd E_sThe two changes over time, and is determined by following relational expressions：

μ in formula_p,sIt is | 1>-|e>With | 0>-|e>The transition dipole moment of optical transition；Ω_p,sIt is the Rabi frequency of two light pulses；C It is the Rabi frequency Ω from light pulse_p,sTo radio signal amplitude E_p,sConversion coefficient, determined by experimental system；Rabi frequency Ω_p,sIt is shown below dependent on time t：

In formulaWithIt is function β (t) and γ (t) time differentials；Wherein γ (t) be superimposed by a series of Fourier components and At：

T in formula_fIt is the duration of pulse (unit is the second)；N is positive integer；a_nIt is the coefficient of corresponding Fourier components, β (t) is depended on γ (t) is shown below：

4. the light pulse generation method according to claim 3 for creating the arbitrary superposition state of three-lever system quantum bit, All a in formula (4)_nValue is zero.

5. the light pulse generation method according to claim 3 for creating the arbitrary superposition state of three-lever system quantum bit, A in formula (4)_nAll even items and odd term meet the following conditions respectively：

a₁+3a₃+5a₅+7a₇=0,

a₂+2a₄+3a₆+4a₈=-0.5.

6. the light pulse generation method according to claim 3 for creating the arbitrary superposition state of three-lever system quantum bit, By scanning a_nValue, light pulse and quantized system effect end time, detection generate target state fidelity and to the back of the body The off-resonance excitation of scape ion obtains a in formula (4) with the variation relation of frequency detuning_nOptimal value.

7. the light pulse generation method according to claim 6 for creating the arbitrary superposition state of three-lever system quantum bit, a_1.3.5.7=0, a₂=-1.10, a₄=0.09, a₆=0.06 and a₈=0.06.

8. generating target state from the arbitrary superposition state of initial quantum bit | 1>The light pulse method of state, done in three-lever system as Lower variation：t→t_f- t, Ω_p,s→-Ω_p,s, it is in Back Up at any time by the amplitude of two light fields, while position mutually increases by 180 Degree.

9. generating rare earth ion quantum device made of light pulse according to one of claim 1-8 the methods.