Quantum state readout using stimulated emission

Abstract

Quantum state readout of atoms is performed using stimulated emission, for example, by irradiating the atoms with electromagnetic radiation (EMR) having a wavelength selected to stimulate photon emission from the atoms. Such emission can be stimulated using four-wave mixing, in which three illumination wavelengths are mixed to stimulate the emission wavelength. The illumination wavelength is detuned from nearby resonance wavelengths to avoid capture by atomic orbitals, which would lead to spontaneous emission rather than stimulated emission. Stimulated emission is directional, facilitating capture of a strong signal. The illumination wavelength can be selected to be in a different direction from the emission wavelength to minimize noise in emission detection. The net result is a high signal-to-noise ratio detection signal and quantum state readout.

Description

CROSS-REFERENCE TO OTHER APPLICATIONS

[0001] This application claims priority to U.S. Patent Application No. 17 / 499,999, filed October 13, 2021, entitled "QUANTUM-STATE READOUT USING FOUR-WAVE MIXING," and U.S. Provisional Patent Application No. 63 / 119,728, filed December 1, 2020, entitled "QUANTUM STATE READOUT AND IMAGING WITH FOUR-WAVE MIXING," both of which are incorporated herein by reference for all purposes. [Background technology]

[0002] While classical digital computers deal with classical units of information (e.g., bits), quantum computers deal with quantum units of information (e.g., qubits). Both classical bits and qubits can be physically represented using two-state carriers. Examples of two-state quantum carriers include electrons, which can be in spin-up and spin-down states, and electrons in atoms, which can be in either a ground state or an excited state. Classical two-state carriers can be in one of two states at any time, while quantum two-state carriers can be in a quantum superposition of both states simultaneously.

[0003] Once the quantum computation is complete, the result can be read out. Regardless of the underlying quantum technology (e.g. superconducting circuits, ions, cold neutral atoms), the superposition state decays probabilistically to a non-superposition state. In effect, the qubits are reduced to bits. The objective is therefore to determine the non-superposition state (i.e., eigenstate) of each quantum state carrier.

[0004] For example, a cold atom quantum array may be read out using fluorescence. Fluorescence may occur when excited state electrons spontaneously emit photons during relaxation to the ground state or at least to a less excited state. To distinguish between atoms in a first quantum state representing a logic 1 (for example) and atoms in a second quantum state representing a logic 0, atoms in the array may be illuminated with light selected to excite only the former to a fluorescence-enabled state. When atoms in a fluorescence-enabled state emit photons, an image of the array may be formed. The image may then show which array locations hold atoms representing a logic 1 and which do not. However, misreading may occur due to a low signal-to-noise ratio in the image. Thus, there is a need for a readout approach that achieves a higher signal-to-noise ratio than existing quantum state readout approaches. [Brief description of the drawings]

[0005] [Figure 1] Schematic diagram showing a quantum state readout system based on stimulated emission.

[0006] [Diagram 2] Schematic illustrating the impact of momentum conservation in the context of stimulated four-wave mixing readout.

[0007] [Diagram 3] 2 is a flow chart illustrating a quantum state readout process that can be implemented in the system of FIG. 1 and other systems.

[0008] [Figure 4] FIG. 1 is a schematic diagram showing a quantum state readout system that uses two stimulated four-wave mixing systems, one for each of two quantum states that represent a binary value.

[0009] [Diagram 5] FIG. 1 is a schematic diagram illustrating a quantum state readout system that uses a dual stimulated four-wave mixing system to provide positive detection for each of two quantum states that represent a binary value.

[0010] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0011] The present invention provides quantum state readout using stimulated emission of electromagnetic radiation (EMR) (e.g., visible and near infrared light). Stimulated emission tends to be highly directional, facilitating capture of a high percentage of emitted photons. A high percentage of captured emission results in a strong emission detection signal. Furthermore, the illumination wavelength and angle of incidence can be selected to facilitate spatial separation of the stimulating illumination from the stimulated emission, leading to low noise capture. In combination, the high percentage capture and excellent rejection of the illumination wavelength provide a high signal-to-noise ratio and improved readout performance.

[0012] As used herein, "stimulated emission" is distinguished from "spontaneous emission." Stimulated emission occurs simultaneously with irradiation, such that the direction of emission is based on the direction of irradiation, due to momentum conservation. Spontaneous emission occurs after a random delay relative to irradiation, such that momentum conservation applies separately to irradiation and emission events. As a result, the emission direction can be in any direction, since it is independent of the irradiation direction. The omnidirectional nature of spontaneous emission makes it difficult to capture a large percentage of the emission, whereas the directionality of stimulated emission allows for a high capture rate and an associated strong signal.

[0013] Emission can be stimulated using a single photon or multiple photons. In the latter case, the multiple photons can include photons of different directions and wavelengths. The present invention also provides for emission of different directions and wavelengths. The embodiment of FIG. 1, for example, utilizes stimulated emission four-wave mixing with three illumination wavelengths with respective directions and one emission wavelength with a direction determined by the three illumination wavelengths.

[0014] As shown in FIG. 1, the quantum state readout system 100 includes a laser system 102, a photodetector 104, and an image analyzer 106 to perform stimulated emission four-wave mixing. The quantum state carriers (QSCs) to be read out are read out from a system (e.g., a cold neutral rubidium-87 ( 87 Rb) atom 110. Atom 110 has a number of eigenstate energy levels (also called "orbitals") that its outer shell electrons can occupy, as shown below: eigenstate energy level |0>, which is used to represent a logic 0, eigenstate energy level |1>, which is used to represent a logic 1, and reference eigenstate energy levels |a>, |b>, and |c>.

[0015] The laser system 102 directs light of wavelength λ 1 toward the atoms 110 along each direction. 1 , λ 2 , and λ 3 For purposes of illustration, the electromagnetic radiation (EMR) has a wavelength λ 1 may be considered to trigger an up-transition of an electron from an eigenstate energy level |1> to a non-eigenstate (non-orbital) energy level |a′> that is non-resonant with the eigenstate |a>, and the EMR with wavelength λ 2 may be considered to trigger an up-transition of an electron from a non-eigenstate energy level |a'> to a non-eigenstate energy level |b'> that is non-resonant with the eigenstate energy level |b>, and the wavelength λ 3 may be considered to trigger the down-transition of an electron from a non-eigenstate energy level |b'> to a non-eigenstate energy level |c'> that is non-resonant with the eigenstate energy level |c>. The atom 110 is excited by a light having a wavelength λ 1 , λ 2 , and λ 3 By "mixing" 4 = λ 1 +λ 2 -λ 3 This produces an EMR of wavelength λ 1 , λ 2 , and λ 3 The atom 110 is emitted in response to irradiation by the

[0016] Rubidium 87( 87 Examples of Rb) atoms are |0>=|5s1 / 2,F=2,m=0>, |1>=|5s1 / 2,F=1,m=0>, |a>=|5p3 / 2,F=2>, |b>=|6s1 / 2,F=1>, and |c>=|5p1 / 2,F=2>. 87 In Rb, the magnitude of the detuning is λ 1 41 megahertz (MHz), λ 2 30MHz for λ 3 These detunings correspond to wavelengths less than one nanometer, and more specifically, in the range of 1 to 10 picometers. 133 Examples of Cs are |0>=|6s1 / 2,F=3,m=0>, |1>=|6s1 / 2,F=4,m=0>, |a>=|6p1 / 2,F=4>, |b>=|7s1 / 2,F=4>, |c>=|6p3 / 2,F=5>. The detuning depends on the atom and the transition of interest, but typically results in a wavelength shift of less than the picometer range (0.1-100 picometers).

[0017] Four-wave mixing offers a wealth of options, including choosing how close the irradiation frequency is to the atomic resonance so that the emission can be stimulated rather than spontaneous. Resonant irradiation can result in spontaneous emission rather than directional emission. In the case of spontaneous emission, irradiation and emission are decoupled such that recoil can occur both during absorption and emission of the irradiation as a result of momentum conservation. Recoil can lead to undesirable displacement and heating of the atoms. In the regime where the laser is detuned from resonance, the atoms do not change state during the four-wave mixing process and spontaneous emission is suppressed, which can beneficially reduce heating and increase process efficiency. In the case of stimulated emission, the generation of the fourth wave can be considered as a result of mixing of atomic dipole moments induced to oscillate by the three laser fields.

[0018] Alternatively, the illumination wavelength can be selected to induce one or more transitions to allowed eigenstates / orbitals where spontaneous emission can occur. Because the direction of spontaneous emission is random, it can be difficult to achieve a high capture rate and thus a high signal-to-noise ratio. On the other hand, avoiding the transitions to allowed eigenstates / orbitals using the illumination wavelength leads to highly directional stimulated emission, facilitating a high rate of photon capture and good spatial separation of the emission from the illumination, and thus a strong emission detection signal.

[0019] A strong emission detection signal may be combined with a low illumination noise detection level, which may be achieved by choosing an illumination direction that is different from any emission direction. 87 For the example of Rb, the irradiation wavelength λ 1 = 70 nanometers (nm), λ 2 = 1367 nm, λ 3 = 1324 nm (corresponding momentum vector p → 1 , p → 2 , and p → 3 2) is the emission wavelength λ 4 = 455 nm (momentum vector p → 4 The magnitude of momentum p → i ∝1 / λ i (e.g., i = 1, 2, 3, 4), so the momentum is larger for shorter wavelengths. If we assume that momentum is lost or gained by the atoms themselves, then conservation of momentum means that p → 4 =p → 1 +p → 2 +p → 3 is required. 87 For the example of Rb, the momentum vector p → 4 Momentum vector p for → 1 , p → 1 , and p→ 1 Each angle is α 1 =1.7°,α 2 =-0.55° and α3=-2.25°, and the emission wavelength λ 4 Irradiation wavelength λ from 1 , λ 2 , and λ 3 is sufficient to allow spatial filtering of 100 kb. Of course, further reduction of the illumination detection noise can be achieved with spectral filtering. The combination of strong signal detection and low illumination noise produces a high signal-to-noise ratio.

[0020] Therefore, the photodetector 104 detects the wavelength λ 4 At this location, the photodetector 104 detects a wavelength λ 1 , λ 2 , and λ 3 Since these irradiating wavelengths are outside the path of 4 The noise that affects the detection is very small. The infrared (IR) removal filter 202 is used to remove near-infrared (700 to 1400 nm) irradiation wavelengths, i.e., λ 1 = 780 nm, λ 2 = 1367 nm, and λ 3 Further noise reduction can be achieved by spectrally filtering out the optical components 102, 104, 106, 110, 120, 1324 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2100 nm, 2200 nm, 2300 nm, 2400 nm, 2500 nm, 3200 nm, 3600 nm, 3800 nm, 4000 nm, 4200 nm, 5000 nm, 5200 nm, 6000 nm, 6200 nm, 7000 nm, 8000 nm, 9000 nm, 10000 nm, 11000 nm, 12000 nm, 1324 nm, 1400 nm, 1500 nm, 1600 nm, 1700 nm, 1800 nm, 1900 nm, 2100 nm, 2200 nm, 2324 nm, 2400 nm, 2500 nm, 3244 nm, 3600 nm, 3800 nm, 3800 nm, 4000 nm, 4200 nm, 5 ...

[0021] Thus, stimulated emission four-wave mixing readout methods can produce substantially higher (10-100x) photon flux on the detector because the four-wave mixing light is much more directional than the fluorescence, which is emitted in all directions. Typical practical imaging systems can only collect a fraction (~1-10%) of the fluorescence due to limitations in the collection solid angle. The FWM light field solid angle is much smaller and can therefore be completely collected by those imaging systems resulting in 10-100x higher photon detection, thus requiring a smaller factor than 10-100x to detect the same number of photons.

[0022] 3 and may be implemented in quantum state readout system 100 and other systems, in step 301 a quantum computation or other process transitions a quantum state carrier (QSC) into a quantum state, typically an unknown superposition state. For example, quantum state readout system 100 may function as a quantum computer that generates possible superposition quantum states.

[0023] In quantum computing, the quantum states of QSCs are manipulated so that the QSCs are made to interact. Typically, the quantum computation result is unknown before being read out. The readout process collapses the superposition state so that what is read out is a non-superposition QSC eigenstate (representing a classical realization of the quantum value). The superposition value resulting from the quantum computation can be approximated by repeating the quantum computation many times to obtain a statistical distribution of the readout results.

[0024] In step 302, the QSC is illuminated with one or more sets of illumination wavelengths, for example using laser light. During illumination, the QSC may switch from a superposition quantum state to an eigenstate. Quantum state readout system 100 (FIG. 1) uses one set of three illumination wavelengths to reliably detect one quantum eigenstate. As discussed further below, quantum state readout systems 500 (FIG. 5) and 600 (FIG. 6) each use two sets of three wavelengths to reliably detect two different eigenstates. Additional illumination sets of three or more wavelengths may be used to reliably distinguish between three or more eigenstates.

[0025] The present invention provides stimulated emission using techniques other than four-wave mixing. For example, a single irradiating wavelength can stimulate emission in atoms prepared in an excited state. In what can be called "three-wave mixing", a detuned two-photon transition can be utilized to stimulate emission of a third wavelength. Detuned n-wave stimulation with n>5 can be achieved by using two or more photon transitions instead of the one-photon transition used in four-wave mixing. Any n-wave mixing is possible as long as the system has good nonlinearity to support n processes.

[0026] In step 303, while the QSC is illuminated, the presence or absence of emission at each of the emission wavelengths may be detected (because stimulated emission is simultaneous with illumination). One readout from one photodetector may indicate the presence or absence of one quantum state. One readout from each of two or more photodetectors may indicate the presence or absence of the same number of quantum states. The number of photodetectors required may be reduced by using two-color or multi-color detectors, or by time multiplexing the photodetectors.

[0027] In step 304, a quantum state readout is accomplished based on the detection obtained in step 303. In the quantum state readout system 100, an image analyzer 106 analyzes the readout from the photodetector 104 to determine the quantum state itself and / or the logic value represented by the quantum state. For example, the detected eigenstates of the atoms may be determined and the logic value determined from the energy levels. Alternatively, the quantum state may be in the form of a logic value without intermediate determination of electronic energy levels. In either case, a determination of the result of the quantum computation may be completed.

[0028] Cold atom quantum computing requires the readout of an atom at each quantum register site. Since there may be a large number of atoms, there is a risk that an atom will vacate the site. In view of this risk, it cannot be assumed that a site that does not have an atom in one state (e.g., logic 1 state) should have an atom in another state (e.g., logic 0 state). To address this risk, the quantum state readout system 400 shown in FIG. 4 provides positive / bright discrimination of a first (e.g., logic 1) state and a second state (e.g., logic 0 state), while negative / dark (or double bright) detection indicates an error condition.

[0029] The quantum state readout system 400 includes: 87 The quantum state readout system 400 includes a logic 1 readout subsystem 430 and a logic 0 readout subsystem 440 designed to read out Rb atoms 450. The logic 1 readout subsystem 430 includes a “logic 1” laser system 432 and a “logic 1” photodetector 434, and the logic 0 readout subsystem 440 includes a “logic 0” laser system 442 and a “logic 0” photodetector 444. More generally, the quantum state readout system 400 includes a laser system 452 that includes laser systems 432 and 442, and a photodetector system 454 that includes photodetectors 434 and 444.

[0030] The logic 1 laser system 432 emits light at a wavelength λ 11 , λ 12 , and λ13 The wavelengths and their respective directions are: 87 Under the condition that Rb atom 450 is in a logic 1 state, the atom 450 is photoinduced at wavelength λ in a direction that is detectable by logic 1 photodetector 434. 14 The logic 0 laser system 442 is selected to emit a wavelength λ 01 , λ 02 , and λ 03 The wavelengths and their respective directions are: 87 When Rb atom 450 is in a logic 0 state, the atom 450 is photoinduced at wavelength λ 2 in a direction that is detectable by logic 0 photodetector 444 . 04 is selected to emit

[0031] The detection signals output by photodetectors 434 and 444 are sent to a detection processor represented in Figure 5 by a readout table 460. As shown by table 460, a detection from logic 1 photodetector 434 in combination with a non-detection from logic 0 photodetector 444 results in: 87 It is shown that the Rb atom 450 was in its logic 1 state (e.g., represented a logic 1). The combination of a detection from the logic 0 photodetector 544 and a non-detection from the logic 1 photodetector 434: 87 It is shown that the Rb atom 450 was in its logic 0 state (e.g., represented a logic 0). No detection from both photodetectors 434 and 444 indicates an error ε state, such as a missing atom. Detection from both photodetectors 434 and 444 also indicates an error state. When a series of atoms is examined, a binary string can be obtained to be interpreted according to the context.

[0032] Quantum state readout system 500 shown in Figure 5 is a variation of quantum state readout system 400, but eliminates the need for a separate laser system to address the second state of interest (e.g., logic 0 laser system 442 of Figure 4). Logic 1 laser system 432 has been modified to include three beam splitters 502, which emit light at wavelengths λ 11, λ 12 , and λ 13 These copies are scaled by an amount determined by the respective frequencies received by the 3× frequency generator 506, with the wavelength λ 11 , λ 1 2, and λ 13 The resulting light is then input to a set of three respective electro-optic modulators 504 which shift the wavelengths λ 01 , λ 02 , and λ 03 . System 500 utilizes a three-level readout table 560 to allow for the possibility that some intermediate photodetection results may not qualify as a clear Yes (1) or No (0). As shown, all but two combinations of readouts represent error conditions. In other respects, system 500 is identical to system 400. Laser system 432, 3×EOM 504, and 3×frequency generator 506 may be considered to comprise a laser super-system 552.

[0033] Another quantum state readout system, not shown here, uses only one laser system and one photodetector. The laser system comprises the 3×EOM and 3×frequency generator of system 500. In this embodiment, the frequency generator oscillates between two frequencies (or between off and on) to time-division multiplex the illumination and mixing wavelengths. The output of the photodetector is demultiplexed into separate readouts for different quantum states (e.g., logic 1 and logic 0).

[0034] As used herein, a "quantum state carrier" or "QSC" is any entity that can assume two or more quantum states, including eigenstates and superpositions of those eigenstates. A QSC can transition between quantum states. A quantum state includes eigenstates (e.g., stable states including those used to represent logic 0 and logic 1) and superpositions of eigenstates. For example, hyperfine levels of the ground state can be considered to be different quantum states. Examples of QSCs include charged and neutral molecular entities, superconducting electronic circuits, quantum dots, and nitrogen-vacancy centers in diamond lattices. More specifically, neutral and charged rubidium, cesium, strontium, and yttrium atoms can function as QSCs. As used herein, "molecular entity" is used as defined in the International Union of Pure and Applied Chemistry (IUPAC) Gold Book to mean: "Any structurally or isotopically distinct atoms, molecules, ions, ion pairs, radicals, radical ions, complexes, conformers, etc. that are identifiable as individually distinguishable entities."

[0035] A QSC can represent a unit of quantum information (e.g., a qubit and other quantum bits). (As used herein, a "qubit" is defined as a unit of quantum information in the sense of the unit x.) R 2 +x i 2 = 1, where x is the unit of quantum information that can be represented by a complex value x. R is the real component of x, and i is the imaginary component of x, and a "qubit" is a value from the set of only natural numbers d of its eigenstates and superpositions).

[0036] As used herein, "electromagnetic radiation" (EMR) spans wavelengths from 1 picometer (pm) to 100 kilometers (km). The wavelengths most relevant to QSC in the form of molecular entities are in the range of 100-10,000 nm, including near ultraviolet light (~300-~400 nm), visible light (~400 nm-~700 nm), and near infrared light (~700-~1400 nm). As used herein, an EMR wavelength is "resonant" with respect to a QSC if it can include transitions between eigenstates of the QSC. As used herein, an EMR wavelength is "detuned" from a resonant wavelength if it is not equal to the resonant wavelength but is within 1% of the resonant wavelength.

[0037] As used herein, "cold" refers to a temperature below 1 millikelvin (1 mK) and "ultra-cooled" characterizes a particle temperature below 100 μK (the typical Doppler cooling limit). Depending on the embodiment, ultra-cooled particles can be even lower, below 100 nanokelvin (nK). For example, in one example of a BEC, the temperature can be about 50 nK. As used herein, "ultra-high vacuum" and "UHV" refer to temperatures below 10 -9 Torr means pressure below 100 MPa.

[0038] The present invention has been described in the context of using four-wave mixing to achieve stimulated emission, in some embodiments other techniques may be used to achieve stimulated emission for purposes of performing quantum state readout and / or for other purposes.

[0039] In this specification, any technology indicated as "prior art" is recognized as prior art, and any technology not indicated as "prior art" is not recognized as prior art. The embodiments shown in the drawings, their modifications, and variations are provided by the present invention, the scope of which is defined by the following claims. [Application Example 1] A quantum state readout process, irradiating a quantum state carrier (QSC) with electromagnetic radiation (EMR) characterized by an illumination set of illumination wavelengths, the illumination with the EMR inducing the QSC to emit EMR at a respective emission wavelength if the QSC was in a first eigenstate during the illumination; Detecting whether EMR at said emission wavelength is emitted from said QSC; determining whether the QSC was in the first eigenstate based on the detection; A process comprising: [Application Example 2] A quantum state readout process as described in Application Example 1, further comprising transitioning the QSC to a superposition state prior to the irradiation, wherein the QSC switches from the superposition state to the eigenstate during the irradiation. [Application Example 3] A quantum state readout process according to Application Example 1, wherein at least one of the irradiation wavelengths is detuned from a resonant wavelength of the QSC. [Application Example 4] The quantum state readout process according to Application Example 1, wherein the emitted EMR has a direction different from each of the directions of the incident EMR. [Application Example 5] A quantum state readout process as described in Application Example 1, wherein there are three irradiation wavelengths, each irradiation wavelength is detuned from a respective resonant wavelength of the QSC by an amount in the range of 0.1 to 100 picometers, each irradiation wavelength has a respective irradiation direction different from the direction of the emitted EMR, the QSC is an atom, and the wavelengths are in a range including near-infrared light and visible light. [Application Example 6] A quantum state readout system, an illumination system for irradiating a quantum state carrier (QSC) with electromagnetic radiation (EMR) characterized by an illumination set of illumination wavelengths, said irradiating EMR inducing said QSC to emit EMR at a respective emission wavelength when said QSC is in a first eigenstate during said illumination; a detector system for detecting whether EMR at said emission wavelength is emitted from said QSC; an analyzer for determining whether the QSC was in the first eigenstate based on said detection; A system comprising: [Application Example 7] A quantum state readout system as described in Application Example 6, further comprising a quantum computer for transitioning the QSC to a superposition state, wherein the QSC switches from the superposition quantum state to the eigenstate during the irradiation. [Application Example 8] A quantum state readout system according to Application Example 6, wherein at least one of the wavelengths is detuned from a resonant wavelength of the QSC. [Application Example 9] A quantum state readout system according to Application Example 6, wherein the emission wavelength has a different direction from each of the directions of the irradiated EMR. [Application Example 10] A quantum state readout system as described in Application Example 6, wherein the illumination system irradiates with three illumination wavelengths, each illumination wavelength being detuned from a respective resonant wavelength of a QSC by an amount in the range of 0.1 to 100 picometers, each illumination wavelength having a respective illumination direction different from the direction of the emitted EMR, the QSC is an atom, and the wavelengths are in a range including near-infrared light and visible light.

Claims

1. A method for reading out a quantum state, comprising the steps of: irradiating a quantum state carrier (QSC) with electromagnetic radiation (EMR) characterized by an illumination set of illumination wavelengths, the illumination with the EMR inducing the QSC to emit EMR at a respective emission wavelength if the QSC was in a first eigenstate during the illumination; Detecting whether EMR at said emission wavelength is emitted from said QSC; determining whether the QSC was in the first eigenstate based on the detection; Equipped with A method, wherein there are three illumination wavelengths, each illumination wavelength is detuned from a respective resonant wavelength of the QSC by an amount in the range of 0.1 to 100 picometers, each illumination wavelength has a respective illumination direction different from the direction of the emitted EMR, the QSC is an atom, and the wavelengths are in a range that includes near infrared light and visible light.

2. 2. The method of claim 1, further comprising: transitioning the QSC to a superposition state prior to the irradiation, the QSC switching from the superposition state to the eigenstate during the irradiation.

3. 2. The method of claim 1, wherein at least one of the illumination wavelengths is detuned from a resonant wavelength of the QSC.

4. 2. The method of claim 1, wherein the emitted EMR has a direction different from each of the directions of the incident EMR.

5. 1. A quantum state readout system comprising: an illumination system for illuminating a quantum state carrier (QSC) with electromagnetic radiation (EMR) characterized by an illumination set of illumination wavelengths, said illumination EMR inducing said QSC to emit EMR at a respective emission wavelength when said QSC is in a first eigenstate during said illumination; a detector system for detecting whether EMR at said emission wavelength is emitted from said QSC; an analyzer for determining whether the QSC was in the first eigenstate based on the detection; Equipped with The illumination system irradiates at three illumination wavelengths, each of which is detuned from a respective resonant wavelength of a QSC by an amount in the range of 0.1 to 100 picometers, each of which has a respective illumination direction that is different from a direction of the emitted EMR, the QSC is an atom, and the wavelengths are in a range that includes near infrared light and visible light.

6. 6. The quantum state readout system of claim 5, further comprising a quantum computer for transitioning said QSC into a superposition state, said QSC switching from said superposition quantum state to said eigenstate during said irradiation.

7. 6. The quantum state readout system of claim 5, wherein at least one of the wavelengths is detuned from a resonant wavelength of the QSC.

8. 6. The quantum state readout system of claim 5, wherein the emission wavelength has a different direction from each of the directions of the illumination EMR.

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