Skip to content
2000
Volume 2, Issue 1
  • ISSN: 2772-3348
  • E-ISSN: 2772-3356

Abstract

Introduction

In the rapidly developing areas of photonics associated with quantum teleportation of photons, quantum cryptography, and quantum computing, ideas are becoming increasingly relevant about the certain localized states of single or several entangled photons moving in space and time. As is known, in quantum mechanics, localized states of particles can only be described using wave functions in coordinate representation – the corresponding wave packets.

Aims

To explain Young's one- and two-photon experiments using coordinate 6-component quantum mechanical and 1-component quasi-classical photon wave functions.

Methods

The article outlines the method developed in authors' previous work in constructing the 6-component coordinate wave function of free photons in the form of the wave packet (an integral over the entire momentum space and sum over two possible values +1 and -1 of the helicity). The basis functions are the circularly polarized monochromatic waves, corresponding to certain values of the momentum, helicity, and photon energy operators and forming a complete orthonormal set of generalized eigenfunctions of these operators. This photon wave function (PWF) is normalized to the unit probability of finding the photon anywhere in space. Both the basis functions and the coordinate PWF satisfy a Schrödinger-type equation derived from the Maxwell-Lorentz equations written in quantum mechanical form first introduced by Majorana. Then the results of modeling and consideration of the space-time evolution of the wave packet with Gaussian momentum distribution corresponding to the directed photon emission for 80 fs are briefly presented. Further, in view of the possibility of constructing the coordinate PWF, the basic formula for the wave-particle duality of photons and particles is formulated. It is emphasized that the photon is fundamentally different from “ordinary” particles, since, according to the authors, the photon is the result of the propagation of a certain complex spin wave in a physical vacuum, the details of which can only be considered simultaneously with the study of the structure of the physical vacuum at Planckian distances.

Results

Young's one- and two-photon experiments are explained using various options for modeling 6-component coordinate PWFs, including approximate functions corresponding to spherically symmetric and electric dipole photon radiation.

Conclusion

This explanation is illustrated using specific examples of radiation and, at the same time, is compared with numerical simulations for spherically symmetric radiation and the use of 1-component quasi-classical PWFs.

Loading

Article metrics loading...

/content/journals/cphs/10.2174/0127723348341614241206215545
2024-12-23
2025-12-13
Loading full text...

Full text loading...

References

  1. AspectA. GrangierP. RogerG. Experimental realization of einstein-podolsky-rosen-bohm gedankenexperiment: A new violation of Bell’s inequalities.Phys. Rev. Lett.1982492919410.1103/PhysRevLett.49.91
    [Google Scholar]
  2. AspectA. DalibardJ. RogerG. Experimental test of Bell’s inequalities using time-varying analyzers.Phys. Rev. Lett.198249251804180710.1103/PhysRevLett.49.1804
    [Google Scholar]
  3. WeihsG. JenneweinT. SimonC. WeinfurterH. ZeilingerA. Violation of Bell’s inequality under strict Einstein locality conditions.Phys. Rev. Lett.199881235039504310.1103/PhysRevLett.81.5039
    [Google Scholar]
  4. ScheidlT. UrsinR. KoflerJ. RamelowS. MaX.S. HerbstT. RatschbacherL. FedrizziA. LangfordN.K. JenneweinT. ZeilingerA. Violation of local realism with freedom of choice.Proc. Natl. Acad. Sci. USA201010746197081971310.1073/pnas.100278010721041665
    [Google Scholar]
  5. MeraliZ. Quantum ‘spookiness’ passes toughest test yet.Nature20155257567141510.1038/nature.2015.1825526333448
    [Google Scholar]
  6. GröblacherS. PaterekT. KaltenbaekR. BruknerČ. ŻukowskiM. AspelmeyerM. ZeilingerA. An experimental test of non-local realism.Nature2007446713887187510.1038/nature0567717443179
    [Google Scholar]
  7. RomeroJ. LeachJ. JackB. BarnettS.M. PadgettM.J. Franke-ArnoldS. Violation of Leggett inequalities in orbital angular momentum subspaces.New J. Phys.2010121212300710.1088/1367‑2630/12/12/123007
    [Google Scholar]
  8. LeggettA.J. GargA. Quantum mechanics versus macroscopic realism: Is the flux there when nobody looks?Phys. Rev. Lett.198554985786010.1103/PhysRevLett.54.85710031639
    [Google Scholar]
  9. GrangierP. RogerG. AspectA. Experimental evidence for a photon anticorrelation effect on a beam splitter: A new light on single-photon interferences.Europhys. Lett.19861417317910.1209/0295‑5075/1/4/004
    [Google Scholar]
  10. JacquesV. WuE. GrosshansF. TreussartF. GrangierP. AspectA. RochJ.F. Experimental realization of Wheeler’s delayed-choice gedanken experiment.Science2007315581496696810.1126/science.113630317303748
    [Google Scholar]
  11. PeruzzoA. ShadboltP. BrunnerN. PopescuS. O’BrienJ.L. A quantum delayed-choice experiment.Science2012338610763463710.1126/science.122671923118183
    [Google Scholar]
  12. MaX.S. KoflerJ. QarryA. TetikN. ScheidlT. UrsinR. RamelowS. HerbstT. RatschbacherL. FedrizziA. JenneweinT. ZeilingerA. Quantum erasure with causally disconnected choice.Proc. Natl. Acad. Sci. USA201311041221122610.1073/pnas.121320111023288900
    [Google Scholar]
  13. ManningA.G. KhakimovR.I. DallR.G. TruscottA.G. Wheeler’s delayed-choice gedanken experiment with a single atom.Nat. Phys.201511753954210.1038/nphys3343
    [Google Scholar]
  14. MaX. KoflerJ. ZeilingerA. Delayed-choice gedanken experiments and their realizations.Rev. Mod. Phys.201688101500510.1103/RevModPhys.88.015005
    [Google Scholar]
  15. VedovatoF. AgnesiC. SchiavonM. DequalD. CalderaroL. TomasinM. MarangonD.G. StancoA. LuceriV. BiancoG. ValloneG. VilloresiP. Extending Wheeler’s delayed-choice experiment to space.Sci. Adv.2017310e170118010.1126/sciadv.170118029075668
    [Google Scholar]
  16. LundeenJ.S. SutherlandB. PatelA. StewartC. BamberC. Direct measurement of the quantum wavefunction.Nature2011474735018819110.1038/nature1012021654800
    [Google Scholar]
  17. ChrapkiewiczR. JachuraM. BanaszekK. WasilewskiW. Hologram of a single photon.Nat. Photonics201610957657910.1038/nphoton.2016.129
    [Google Scholar]
  18. LandauL. PeierlsR. Quantum electrodynamics in configuration space.Z. Phys.193062188200
    [Google Scholar]
  19. KramersH.A. Quantum MechanicsNorth- HollandAmsterdam1958
    [Google Scholar]
  20. NewtonT.D. WignerE.P. Localized states for elementary systems.Rev. Mod. Phys.194921340040610.1103/RevModPhys.21.400
    [Google Scholar]
  21. BohmD. Quantum Theory.LondonConstable1954
    [Google Scholar]
  22. PowerE.A. Introductory Quantum Electrodynamics.LondonLongmans1964
    [Google Scholar]
  23. BerestetskiiV.B. LifshitzE.M. PitaevskiiL.P. Quantum electrodynamicsNaukaMoscow1982
    [Google Scholar]
  24. AhiezerA.I. BeresteckijV.B. Quantum electrodynamics.MoscowNauka1981
    [Google Scholar]
  25. LevichV.G. VdovinJu. Course of theoretical physics.MoscowNauka1971II
    [Google Scholar]
  26. ChiaoR.Y. KwiatP.G. SteinbergA.M. Quantum and semiclassical optics: Journal of the European Optical Society.Part B19957325927810.1088/1355‑5111/7/3/006
    [Google Scholar]
  27. ScullyM.O. ZubairyM.S. Quantum Optics.CambridgeCambridge Univ. Press199710.1017/CBO9780511813993
    [Google Scholar]
  28. Białynicki-BirulaI. On the wave function of the photon.Acta Phys. Pol. A1994861-29711610.12693/APhysPolA.86.97
    [Google Scholar]
  29. MandelM. WolfE. Optical coherence and quantum optics.CambridgeCambridge Univ. Press199510.1017/CBO9781139644105
    [Google Scholar]
  30. SipeJ.E. Photon wave functions.Phys. Rev. A19955231875188310.1103/PhysRevA.52.18759912446
    [Google Scholar]
  31. DavydovA.P. Quantum mechanics of photon.Science and school: Abstracts of the XXXIII scientific conf. of MSPIPublishing House of MSPI: Magnitogorsk, Russia, 1995, pp. 206-207.
    [Google Scholar]
  32. KlyshkoD.N. Quantum optics: Quantum, classical, and metaphysical aspects.Phys. Uspekhi199437111097112210.1070/PU1994v037n11ABEH000054
    [Google Scholar]
  33. GisinN. RibordyG. TittelW. ZbindenH. Quantum cryptography.Rev. Mod. Phys.200274114519510.1103/RevModPhys.74.145
    [Google Scholar]
  34. ScaraniV. Bechmann-PasquinucciH. CerfN.J. DušekM. LütkenhausN. PeevM. The security of practical quantum key distribution.Rev. Mod. Phys.20098131301135010.1103/RevModPhys.81.1301
    [Google Scholar]
  35. FulconisJ. AlibartO. O’BrienJ.L. WadsworthW.J. RarityJ.G. Nonclassical interference and entanglement generation using a photonic crystal fiber pair photon source.Phys. Rev. Lett.2007991212050110.1103/PhysRevLett.99.12050117930484
    [Google Scholar]
  36. LiangC. Xiao-YingL. Hai-YangF. LeiY. Xiao-XinM. Photonic crystal fiber source of quantum correlated photon pairs in the 1550 nm telecom band.Chin. Phys. Lett.200926404420910.1088/0256‑307X/26/4/044209
    [Google Scholar]
  37. WaksE. InoueK. OliverW.D. DiamantiE. YamamotoY. High-efficiency photon-number detection for quantum information processing.IEEE J. Sel. Top. Quantum Electron.2003961502151110.1109/JSTQE.2003.820917
    [Google Scholar]
  38. ProcházkaI. HamalK. SopkoB. Recent achievements in single photon detectors and their applications.J. Mod. Opt.2004519-101289131310.1080/09500340408235273
    [Google Scholar]
  39. GansenE.J. RoweM.A. GreeneM.B. RosenbergD. HarveyT.E. SuM.Y. HadfieldR.H. NamS.W. MirinR.P. Photon-number-discriminating detection using a quantum-dot, optically gated, field-effect transistor.Nat. Photonics200711058558810.1038/nphoton.2007.173
    [Google Scholar]
  40. JiangL.A. DaulerE.A. ChangJ.T. Photon-number-resolving detector with 10 bits of resolution.Phys. Rev. A200775606232510.1103/PhysRevA.75.062325
    [Google Scholar]
  41. KardynałB.E. YuanZ.L. ShieldsA.J. An avalanche‐photodiode-based photon-number-resolving detector.Nat. Photonics20082742542810.1038/nphoton.2008.101
    [Google Scholar]
  42. Bialynicki-BirulaI. The photon wave function.Coherence and Quantum Optics VII. EberlyJ.H. New YorkPlenum Press199631332310.1007/978‑1‑4757‑9742‑8_38
    [Google Scholar]
  43. Bialynicki-BirulaI. Photon wave function.Progress in Optics. WolfE. AmsterdamElsevier: North-Holland1996XXXVI248294
    [Google Scholar]
  44. HawtonM. Photon wave functions in a localized coordinate space basis.Phys. Rev. A19995953223322710.1103/PhysRevA.59.3223
    [Google Scholar]
  45. DavydovA.P. Photon wave function in coordinate representation.Magnitogorsk State University BulletinMaSU: MagnitogorskRussia2004
    [Google Scholar]
  46. CugnonJ. The photon wave function.Open J. Microphys.2011134152
    [Google Scholar]
  47. SaariP. Photon localization revisited.Quantum Optics and Laser Experiments. LyagushynS. CroatiaInTech – Open Access Publisher2012496610.5772/29895
    [Google Scholar]
  48. DavydovA.P. Quantum mechanics of the photon: Wave function in the coordinate representation.Electromagn. Waves Electron. Syst.20152054361
    [Google Scholar]
  49. DavydovA.P. ZlydnevaT.P. On the relativistic invariance of the continuity equation in quantum mechanics of the photon.International Research Journal20164-64613413710.18454/IRJ.2016.46.145
    [Google Scholar]
  50. DavydovA.P. ZlydnevaT.P. On the photon wave function in coordinate and momentum representations.Int. Res. J.201611415215610.18454/IRJ.2016.53.104
    [Google Scholar]
  51. DavydovA.P. Photon wave function in the coordinate representation.Magnitogorsk, RussiaPublishing House of Nosov MSTU2015
    [Google Scholar]
  52. DavydovA.P. Evolution in space and time of the wave packet of a photon of femtosecond radiation from the point of view of quantum mechanics. Modern problems of science and education Abstracts of XLIII sci. conf. of teachers of MaSUMaGU: Magnitogorsk, Russia, 2005, pp. 269-270.
    [Google Scholar]
  53. DavydovA.P. Modeling the propagation of a photon wave packet in three-dimensional space.Actual problems of modern science, technology and education — materials of the 73rd Intern. scientific and technical conf.Publishing House of Nosov MSTU: Magnitogorsk, Russia, 2015, vol. 3, pp. 133-137.
    [Google Scholar]
  54. DavydovA.P. ZlydnevaT.P. Single-photon approach to the modeling short-pulse laser radiation.Bull. Sci. Educ. North-West Russia20151497111
    [Google Scholar]
  55. DavydovA.P. ZlydnevaT.P. Modeling of short-pulse laser radiation in terms of photon wave function in coordinate representation. Instrumentation engineering, electronics and telecommu-nications — Paper book of the Internat. Forum IEET-2015.Izhevsk, RussiaPublishing House of Kalashnikov ISTU20165163
    [Google Scholar]
  56. DavydovA.P. ZlydnevaT.P. The Young’s interference experiment in the light of the single-photon modeling of the laser radiation.Information Technologies in Science, Management, Social Sphere and Medicine (ITSMSSM 2016) – Proc. of the 2016 Conf,Atlantis Press, January 2016, pp. 208-215.10.2991/itsmssm‑16.2016.100
    [Google Scholar]
  57. DavydovA.P. ZlydnevaT.P. On the reduction of free photons speed in modeling of their propagation in space by the wave function in coordinate representation.2016 13th International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE),Novosibirsk, Russia, 03-06 October 2016, pp. 233-240.
    [Google Scholar]
  58. GiovanniniD. RomeroJ. PotočekV. FerencziG. SpeiritsF. BarnettS.M. FaccioD. PadgettM.J. Spatially structured photons that travel in free space slower than the speed of light.Science2015347622485786010.1126/science.aaa303525612608
    [Google Scholar]
  59. GouesbetG. LockJ.A. On light traveling in free space slower than the speed of light and other curiosities associated to light propagation and light scattering.Available from: http://meetingorganizer.copernicus.org/ELS-XV-2015/ELS-XV-2015-16.pdf
  60. MignaniE. RecamiE. BaldoM. About a dirac-like equation for the photon according to ettore majorana.Lett. Nuovo Cimento1974111256857210.1007/BF02812391
    [Google Scholar]
  61. DavydovA.P. On the elaboration of Special Relativity (SR) proceeding from the space and time symmetry – Without applying the SR postulates.Electromagn. Waves Electron. Syst.2003814958
    [Google Scholar]
  62. DavydovA.P. A course of lectures on quantum mechanics. The mathematical apparatus of quantum mechanics.Magnitogorsk, RussiaNosov MSTU2014
    [Google Scholar]
  63. DavydovA.P. Dispersion interpretation of energy-time uncertainty relation and shot-time impulse laser radiation.Bull. Sci. Educ. North-West Russia201734131145
    [Google Scholar]
  64. DavydovA.P. Possibility of quantum nonsingular black holes with Planck's parameters and extreme metric in physics and cosmology.Electromagn. Waves Electron. Syst.1998326778
    [Google Scholar]
  65. DavydovA.P. The extreme maximons, the structure of the fundamental particles, quantum electrodynamics, general relativity and Logunov's relativistic theory of gravitation.Electromagn. Waves Electron. Syst.200165413
    [Google Scholar]
  66. DavydovA.P. ZlydnevaT.P. The Modeling of the Young’s interference experiment in terms of single-photon wave function in the coordinate representation. Information technologies in Science, Management, Social sphere and Medicine (ITSMSSM 2017) – Proc. of the IV International research conf.ShenzhenAtlantis Press201772257265
    [Google Scholar]
  67. DavydovA.P. ZlydnevaT.P. On the interference of light from the point of view of the photon wave function in the coordinate representation.Actual problems of modern science, technology and education — materials of the 75rd Intern. scientific and technical conf,Publishing House of Nosov MSTU: Magnitogorsk, Russia, 2017, vol. 2, pp. 109-112.
    [Google Scholar]
  68. DavydovA.P. ZlydnevaT.P. Space-time probability density of detection of a photon in laser beam of the femtosecond range.2018 XIV International Scientific-Technical Conference on Actual Problems of Electronics Instrument Engineering (APEIE)Novosibirsk, Russia, 02-06 October 2018, pp. 58-69.
    [Google Scholar]
  69. DavydovA.P. ZlydnevaT.P. Interference of electromagnetic waves from the point of view of photon wave function in coordinate representation.Electromagn. Waves Electron. Syst.20182382740
    [Google Scholar]
  70. DavydovA.P. ZlydnevaT.P. On simulation of the photon wave function to explain the Young’s experiment and prospects for its use in quantum cryptography.J. Phys. Conf. Ser.20201661101202810.1088/1742‑6596/1661/1/012028
    [Google Scholar]
  71. DavydovA.P. ZlydnevaT.P. Analytical modeling of Young's single-photon experiment using quasi-classical and approximate quantum-mechanical coordinate wave functions of photon.Inzhenernaya Fizika202394556
    [Google Scholar]
  72. DavydovA.P. ZlydnevaT.P. Analytical modeling of the Young’s single-photon experiment using the quasi-classical and approximate quantum-mechanical coordinate photon wave functions.Opt. Spectrosc.2023131111148115610.1134/S0030400X24700140
    [Google Scholar]
  73. ClauserJ.F. Experimental distinction between the quantum and classical field-theoretic predictions for the photoelectric effect.Phys. Rev. D Part. Fields19749485386010.1103/PhysRevD.9.853
    [Google Scholar]
  74. FeynmanR.P. LeightonR.B. SandsM. The Feynman Lectures on Physics: Quantum Mechanics.Reading, MAAddison-Wesley19653
    [Google Scholar]
  75. TaylorG.I. Interference fringes with feeble light.Proc. Camb. Philos. Soc.190915114115
    [Google Scholar]
  76. QianX.F. AgarwalG.S. Quantum duality: A source point of view.Phys. Rev. Res.20202101203110.1103/PhysRevResearch.2.012031
    [Google Scholar]
  77. YoonT.H. ChoM. Quantitative complementarity of wave-particle duality.Sci. Adv.2021734eabi926810.1126/sciadv.abi926834407933
    [Google Scholar]
  78. TurekY. RenY.F. Separating the wave and particle attributes of two entangled photons.Preprints 2312.013162023
    [Google Scholar]
  79. JönssonC. Electron interference at several artificially created fine slits.Z. Phys.1961161445447410.1007/BF01342460
    [Google Scholar]
  80. TonomuraA. EndoJ. MatsudaT. KawasakiT. EzawaH. Demonstration of single-electron buildup of an interference pattern.Am. J. Phys.198957211712010.1119/1.16104
    [Google Scholar]
  81. HackermüllerL. HornbergerK. BrezgerB. ZeilingerA. ArndtM. Decoherence of matter waves by thermal emission of radiation.Nature2004427697671171410.1038/nature0227614973478
    [Google Scholar]
  82. FeinY.Y. GeyerP. ZwickP. KiałkaF. PedalinoS. MayorM. GerlichS. ArndtM. Quantum superposition of molecules beyond 25 kDa.Nat. Phys.201915121242124510.1038/s41567‑019‑0663‑9
    [Google Scholar]
  83. DenkmayrT. GeppertH. SponarS. LemmelH. MatzkinA. TollaksenJ. HasegawaY. Observation of a quantum Cheshire Cat in a matter-wave interferometer experiment.Nat. Commun.201451449210.1038/ncomms549225072171
    [Google Scholar]
  84. DiracP.A.M. The Principles of Quantum Mechanics.Fourth ed., revisedOxfordClarendon Press1967
    [Google Scholar]
  85. DavydovA.P. ZlydnevaT.P. On the wave-particle duality within the framework of modeling single-photon interference.J. Phys. Conf. Ser.20191399202201910.1088/1742‑6596/1399/2/022019
    [Google Scholar]
  86. DavydovA.P. ZlydnevaT.P. Single- and two-photon interference within the simulated photon wave function in coordinate representation.J. Phys. Conf. Ser.20201679202205110.1088/1742‑6596/1679/2/022051
    [Google Scholar]
  87. DavydovA.P. ZlydnevaT.P. Simulation of the two-photon Young's experiment in the framework of the photons quantum mechanics and in the quasi-classical approach in the electric dipole approximation.Inzhenernaya Fizika202261523
    [Google Scholar]
  88. DavydovA.P. ZlydnevaT.P. Simulation of the two-photon Young’s experiment within the framework of the photon quantum mechanics and in the quasi-classical approach in the electric-dipole approximation.Opt. Spectrosc.2023131111157116310.1134/S0030400X24700152
    [Google Scholar]
  89. DavydovA. ZlydnevaT. On numerical modeling of the Young’s experiment with two sources of single-photon spherical coordinate wave functions.Lecture Notes in Networks and Systems202242432733510.1007/978‑3‑030‑97020‑8_30
    [Google Scholar]
  90. DavydovA.P. DolgushinD.M. ZlydnevaT.P. FaizrakhmanovN.R. Single- and two-photon Young's experiments from the point of view of Feynman amplitudes, Green functions and photon coordinate wave functions.Inzhenernaya Fizika202413248
    [Google Scholar]
  91. DavydovA.P. DolgushinD.M. ZlydnevaT.P. FaizrakhmanovN.R. Young’s single- and double-slit experiments in terms of the Feynman amplitudes, Green’s functions, and photon coordinate wave functions.Opt. Spectrosc.2023131111164117710.1134/S0030400X24700164
    [Google Scholar]
  92. DavydovA.P. ZlydnevaT.P. On numerical and approximate analytical modeling of single- and two-photon Young's experiment using the photon coordinate wave function.E3S Web Conf.20244740202610.1051/e3sconf/202447402026
    [Google Scholar]
  93. DavydovA.P. ZlydnevaT.P. Two-photon interference from two independent sources in the scheme of Young's experiment in the framework of modeling the coordinate wave function of the photon.Inzhenernaya Fizika202111915
    [Google Scholar]
  94. SmithB.J. KillettE. RaymerM.G. WalmsleyI.A. BanaszekK. Measurement of the transverse spatial quantum state of light at the single-photon level: publisher’s note.Opt. Lett.20214692151215110.1364/OL.42709633929435
    [Google Scholar]
  95. MirhosseiniM. Magaña-LoaizaO.S. Hashemi RafsanjaniS.M. BoydR.W. Compressive direct measurement of the quantum wave function.Phys. Rev. Lett.2014113909040210.1103/PhysRevLett.113.09040225215964
    [Google Scholar]
  96. LamB. ElKabbashM. ZhangJ. GuoC. Spatial wavefunction characterization of femtosecond pulses at single-photon level.Research202020202020/242101710.34133/2020/242101732607496
    [Google Scholar]
  97. DevrariV. SinghM. Quantum double slit experiment with reversible detection of photons.Sci. Rep.20241412043810.1038/s41598‑024‑71091‑139227623
    [Google Scholar]
  98. QureshiT. Understanding modified two-slit experiments using path markers.Found. Phys.20235323810.1007/s10701‑023‑00684‑z
    [Google Scholar]
  99. LiJ.K. SunK. WangY. HaoZ.Y. LiuZ.H. ZhouJ. FanX.Y. ChenJ.L. XuJ.S. LiC.F. GuoG.C. Experimental demonstration of separating the wave‒particle duality of a single photon with the quantum Cheshire cat.Light Sci. Appl.20231211810.1038/s41377‑022‑01063‑536599829
    [Google Scholar]
/content/journals/cphs/10.2174/0127723348341614241206215545
Loading
/content/journals/cphs/10.2174/0127723348341614241206215545
Loading

Data & Media loading...

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error
Please enter a valid_number test